modern test & measure: may 2014

May 2014

Teledyne LeCroy's Powerful Test Equipment Meets the Industry's Ever-changing Demands

RAISING THE BAR:

Low-cost DDR3 Analysis

Understanding Probe Calibration

Interview with David Graef, CTO of Teledyne LeCroy

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READY TO LAUNCH

For the launch of the Tiva C Series Connected LaunchPad, TI has partnered with Exosite, mentioned briefly above, to provide easy access to the LaunchPad from the Internet. The LaunchPad takes about 10 minutes to set up and you can immediately interact with it across the Internet and do things like turn an LED on and off remotely from the website and see the reported temperature as well. It can also display approximate geographic location based on the assigned IP address and display a map of all other connected LaunchPad owners if they are active and plugged-in to Exosite. “In addition, it supports a basic game by enabling someone to interface to the Connected LaunchPad through a serial port from a terminal while someone else is playing with them through their browser. It is basically showing how you can interact remotely with this product and a user even if you are across the globe,” Folkens explained.

START DEVELOPING

The Tiva C Series Connected LaunchPad is shipping now and the price is right; at $19.99 USD, it is less than half the price of other Ethernet-ready kits. The LaunchPad comes complete with quick start and user guides, and ample online support to ensure developers of all backgrounds are well equipped to begin creating cloud-based applications. “We have assembled an online support team to monitor the Engineering-to-Engineering (or E2E) Community,” Folkens said. “Along with this, you also got a free Code Composer Studio Integrated Development Environment, which allows developers to use the full capability. We also support other tool chains like Keil, IAR and Mentor Embedded.

Affordable, versatile, and easy to use, the Tiva Series Connected LaunchPad is well suited for a broad audience and promises to facilitate the expansion of ingenious IoT applications in the cloud. As Folkens concluded, “The target audiences actually are the hobbyists, students and professional engineers. A better way of looking at it is that we are targeting people with innovative ideas and trying to help them get those ideas launched into the cloud.”

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Modern Test & Measure CONTENTS

4 TECH ARTICLEUnderstanding Probe Calibration Methods

3

What would you do if you were confronted with the following problems?

Scenario 1: The heating system failed to start at 4.00am this morning – again! When tested, everything seems to work fine, but the office staff are becoming really annoyed at having to work wearing coats and gloves to keep warm for the first three hours each morning. The problem is that it only goes wrong during the night, and then only once or twice a week.

Scenario 2: Unmanned railroad crossings use automatic barriers to protect the track when a train approaches. The control systems are designed for maximum reliability and fail safe operation for obvious reasons. As with all control systems, they are dependent on the correct operation of sensors and other external control signals. One particular crossing failed to open after a train had passed on several occasions, causing considerable delay and frustration to the road traffic. The fault was intermittent and by the time an electrician had arrived on site, the crossing was working correctly. The control unit was replaced on two occasions, but the problem persisted.

Scenario 3: An automatic valve assembly machine has four stations, multiple heads and several sensors. Occasionally, about twice a month, it gets out-of-step and starts to misplace vent seals. The many control

and sensor signals are all switching away at such a rate that is impossible to clearly see what is happening, especially as timing and sequencing is all important. Stepping the machine in slow sequence did not show any problem. Using a conventional data logger was not an option because the signals varied from 12v dc to 240v ac and included 24v ac and dc, plus 110v ac.

Scenario 4: The captain of a rig support vessel reported that he had experienced momentary rogue operation of a rear thruster unit. These are used when maneuvering in dock or in close proximity to a gas rig. Inadvertent operation could have very serious and potentially disastrous consequences. Initial thoughts were that the problem must lie with the thruster control rack, down at the rear of the engine room.

Scenario 5: Staff at a high security establishment wanted to run a monitoring program to record the number of times doors were opened/shut over an extended time period. Statistical information related to door opening sequences was also required. The doors, of which there were 27, were controlled and monitored from acentral office.

Fortunately there is a device that can solve all of these problems. Made in Europe, FTR- Birdie is a compact, rugged, yellow polycarbonate shock-resistant case (9.85” x 6.5” x 2.4”) weighing only 2lb, whose inputs are double-insulated with interlocked access for additional safety. It can be connected to a maximum of 16 key points on a problematicelectrical system. The solid-state, isolated input channels are fused for maximum reliability and safety, and the input on/off status of each line is displayed by bright LED indicators and on an LCD display. A wide input

range of voltages can be monitored, from 12V to 240Vac/dc, without any need to program, select, or configure the inputs.

FTR-Birdie captures the time and date of up to 32768 line events (auto stop or overwrite) on 16 lines, which can later be replayed step-by-step for evaluation. The display shows the line states and the previous 40 changes that have occurred, so it is easy to see what preceded fault conditions and understand exactly what happened within the control system.

FTR-Birdie records exactly what happened, when and in what order, so that faults can be traced quickly. It can produce savings in operator investigation time and avoid unnecessary ‘swap-outs’. Its recording mode permits unattended operation and is ideal for detecting intermittent electrical faults.

The Faraday cup (Figure 3) method can be used to measure the static charge on a wide range of substances and objects, such as plastics, films, liquids, gases, and electronic components.

A Faraday cup (also called a Faraday cage or icepail) is usually made of sheet metal or conductive mesh. The electric field within a closed, empty conductor is zero, so the cup shields the object placed inside it from any atmospheric or stray electric fields. This enables the accurate measurement of the charge.A Faraday cup consists of two electrodes, one inside the other, separated by an insulator. The inside electrode is connected to the electrometer HI and the outside electrode is connected to the electrometer LO. When a charged object is placed within the inside electrode, an induced charge will flow into the electrometer.

A Faraday cup can have virtually any dimensions, depending on the size and shape of the object to be tested. Cylindrical and spherical shapes are typically the most convenient choices—simple containers such as coffee or paint cans are often used. The electrodes can be made of any conductive material. The support insulators should be made of materials with very high resistance, such as Teflon® or ceramic. For convenience in making connections, mount a BNC connector on the outside electrode. Connect the outer or shield connection of the BNC connector to the outside electrode, then connect the inner conductor of the BNC connector to the inside electrode. Use an adapter to connect the BNC connector to the triax input of the electrometer.

Figure 3. A Faraday Cup

CONCLUSION

Ensuring the accuracy of charge measurements requires careful attention to creating appropriate system configurations and following good measurement practices consistently. With the right instrumentation and a good understanding of the principles involved, you can obtain high integrity measurements consistently. Do you have any question about the material in this blog? Please contact me at [email protected].

To measure the static charge on an object, connect an electrometer to the Faraday cup using a shielded cable. Turn on the electrometer, select the coulombs function, then disable “Zero Check” and press “Rel” to zero the display. Drop the charged object to be tested into the Faraday cup. Note the charge reading on the electrometer immediately; don’t wait for the reading to settle because the input offset current of the electrometer will continue charging the input of the meter. This is particularly important when the unknown charge is at the pico-coulomb level. If the object is conductive, it will be discharged as soon as it touches the electrode. Enable “Zero Check” to re-zero the meter in preparation for the next measurement.

With the right instrumentation and a good understanding of the principles involved,

you can obtain high integrity

measurements consistently.

The Faraday cup (Figure 3) method can be used to

measure the static charge on a wide range of substances

and objects, such as plastics, films, liquids, gases, and electronic components.

6 TECH ARTICLEFinding Electrical Control System Faults

14TECH ARTICLE

Good Measurement Practices Part 3:Common Charge Measurement Applications

Teledyne LeCroy is a leading provider of high-end test and measure equipment. The company’s oscilloscope and protocol analyzer product

areas help tackle the toughest test applications out there, offering tailored solutions to meet the user’s needs. The use of serial data communications technologies in the industry has made the company refocus their efforts to explore this burgeoning field, yielding a new line of serial data analysis tools.

We spoke with David Graef, CTO of Teledyne LeCroy, about the benefits of merging Teledyne and LeCroy, the current SI challenges in the industry, and their new line of extremely powerful scopes.

RAISING THE BAR:Teledyne LeCroy’s Powerful Test Equipment Meets the Industry’s

“We are producing the highest quality, most accurate, precision measurements that people can get, because that’s the expectation.”

EVER-CHANGING DEMANDSInterview with David Graef - CTO of Teledyne LeCroy28 COVER INTERVIEW

David Graef - CTO of Teledyne LeCroy

To support the goal of reducing the cost of these measurements, the DDR3 decoder in the solution has

been modified to work from address and command signals only, thus reducing total channel count necessary for meaningful measurements. For example, the new Agilent 16850 Series entry level 34-channel system can perform DDR3 1333 address and command state (synchronous) measurements and analysis for around $36K; in the past, a logic analyzer solution that could offer such measurements and analysis required a budget of around $100K.

DDR3 BGA interposers contain a buried tip resistor to isolate the DRAM system from the logic analyzer probing. Such a probing scheme is workable up to DDR3 rates of 2500 Mbit per second. This setup provides plenty of margin for the DDR3 1333 measurements made by low cost logic analyzers.

Other probing options include the use of either a DIMM interposer or a mid-bus probe. Mid-bus probing involves placing connection pads or a connector somewhere along the PC board memory traces between the IC containing the memory controller and the memory ICs. A probe then touches those pads or plugs into the connector to get access to the DDR3 signals.

A BGA probe offers the advantage that no special PC board modifications are required other than ensuring that there is enough keep out volume (kov) for the probe to fit. In addition, logic analyzers come with setup files when using such probes.

Probing requirements for DDR3 measurementsIn order to make real-time measurements on the interface between the DDR3 memory controller and memory devices, it is necessary to probe signals in a way that does not cause significant distortion but instead provides an accurate picture of those signals. A good probing option for designs with embedded memories is the use of BGA probes as shown in Figure 1. Address, command and data signals are intercepted and brought by coaxial ribbon cable to the logic analyzer.

DDR3 bus decodeOne analysis tool that helps a designer to better understand how their external DDR3 memory is actually behaving is a memory decoder. This software takes raw acquired address and command state signals and converts them into a much more easily understood format, as shown in Figure 2. Memory commands like “Writes” and “Reads” are displayed along with related Chip Select, Bank Address, Row Address, and Column Address

information. Other commands like “Activates” and “Deselects” are shown. This state-mode trace capture is stored in deep memory so it reflects a significant amount of target activity time. Low cost logic analyzers have a maximum input clock frequency of 700 MHz, which allows the state capture of 667 MHz address and command signals on DDR3 1333 memories.

Figure 1. x8 DDR3 BGA probe connection

Figure 2. Memory decoder trace of DDR3 address and command lines

“One analysis tool that helps a designer to better understand how their external DDR3 memory is actually behaving is a memory decoder.”

36 TECH ARTICLELow Cost DDR Decode & Analysis

44

Modern Test & Measure

Understanding ProbeCalibration MethodsIf there’s a topic concerning probes that causes confusion, questions, and misunderstandings, it’s loading. It would be a much simpler world if attaching a probe to a circuit under test had no effect on either the signal being measured or the device the probe is connected to. Unfortunately, the world isn’t quite so simple.

Like it or not, attaching an oscilloscope probe to a circuit invokes certain constraints imposed by fundamental laws of physics: You can't measure something without affecting it. When we try to measure a signal traveling from point A to point B, we are borrowing some of the signal's energy and diverting it to point C (the oscilloscope's front end). We hope that our probe will borrow as little energy as possible and affect the operation of the circuit in minimal fashion.

Because the probe must borrow energy from the signal under test, that probe must have a finite impedance value at all points within its frequency range. The higher the impedance, the smaller the probe's effect on both the signal and the operation of the circuit being tested. However, maintaining high probe impedance as signal frequency rises is a lot easier said than done.

At the end of the day, we know that our probe will exhibit some loading when we apply it to the circuit under test. The important thing to understand is that there are two ways to calibrate a probe and to measure its bandwidth. Knowing which one your equipment uses is critical to your interpretation of your measurement results.

To measure a probe's response, generate a very well-characterized signal, perhaps from a vector network analyzer (VNA). We'll call this signal Vref. Then use your probe to acquire this signal; we'll call the acquired signal Vmeas. The transfer function Vmeas/Vref yields the response of the probe.

Now, the key question at this point is: When we measured Vref, was the probe connected to the circuit or not (Figure 1)? If the probe was connected to the circuit when Vref was

Figure 1: The various measurement points for probe calibration

measured, this is known as an input-referred measurement. Vref was measured with the probe loading in place (let's call this measured value Vprobe). As a result, the transfer function Vmeas/Vprobe relates the voltage present at the scope input to the voltage present at the probe tip. If we apply the resulting correction to the probe, then all signals we acquire with it will be displayed on the oscilloscope along with the probe loading.

If the probe was not connected to the circuit when Vref was measured, we've taken a source-referred measurement. Vref was measured on the original signal without any probe loading in place (call this measured value Vsource). Thus, the transfer function Vmeas/Vsource relates the voltage present at the scope input to the voltage present before the probe was attached. By the way, this corresponds to the insertion loss of the probe.

If we apply the resulting correction to our probe, than all the signals displayed on the oscilloscope will be the original signal without any probe loading.

When making source-referred corrections, one must make an assumption about the source impedance of the device under test. If you use this method to calibrate your probe, the source impedance will be the impedance of the fixture used to connect the probe to the VNA. Almost invariably, this impedance will be 50Ω single-ended or 100Ω differential. This is a reasonable assumption for most real-world, high-bandwidth probing scenarios.

In practice, the difference between these two correction methods as far as the end user is concerned will be minimal if the probe impedance is much greater than the DUT's source impedance.

By David Maliniak Technical Marketing Communication Specialist Teledyne LeCroy

5

TECH ARTICLE

5

Understanding ProbeCalibration MethodsIf there’s a topic concerning probes that causes confusion, questions, and misunderstandings, it’s loading. It would be a much simpler world if attaching a probe to a circuit under test had no effect on either the signal being measured or the device the probe is connected to. Unfortunately, the world isn’t quite so simple.

Like it or not, attaching an oscilloscope probe to a circuit invokes certain constraints imposed by fundamental laws of physics: You can't measure something without affecting it. When we try to measure a signal traveling from point A to point B, we are borrowing some of the signal's energy and diverting it to point C (the oscilloscope's front end). We hope that our probe will borrow as little energy as possible and affect the operation of the circuit in minimal fashion.

Because the probe must borrow energy from the signal under test, that probe must have a finite impedance value at all points within its frequency range. The higher the impedance, the smaller the probe's effect on both the signal and the operation of the circuit being tested. However, maintaining high probe impedance as signal frequency rises is a lot easier said than done.

At the end of the day, we know that our probe will exhibit some loading when we apply it to the circuit under test. The important thing to understand is that there are two ways to calibrate a probe and to measure its bandwidth. Knowing which one your equipment uses is critical to your interpretation of your measurement results.

To measure a probe's response, generate a very well-characterized signal, perhaps from a vector network analyzer (VNA). We'll call this signal Vref. Then use your probe to acquire this signal; we'll call the acquired signal Vmeas. The transfer function Vmeas/Vref yields the response of the probe.

Now, the key question at this point is: When we measured Vref, was the probe connected to the circuit or not (Figure 1)? If the probe was connected to the circuit when Vref was

Figure 1: The various measurement points for probe calibration

measured, this is known as an input-referred measurement. Vref was measured with the probe loading in place (let's call this measured value Vprobe). As a result, the transfer function Vmeas/Vprobe relates the voltage present at the scope input to the voltage present at the probe tip. If we apply the resulting correction to the probe, then all signals we acquire with it will be displayed on the oscilloscope along with the probe loading.

If the probe was not connected to the circuit when Vref was measured, we've taken a source-referred measurement. Vref was measured on the original signal without any probe loading in place (call this measured value Vsource). Thus, the transfer function Vmeas/Vsource relates the voltage present at the scope input to the voltage present before the probe was attached. By the way, this corresponds to the insertion loss of the probe.

If we apply the resulting correction to our probe, than all the signals displayed on the oscilloscope will be the original signal without any probe loading.

When making source-referred corrections, one must make an assumption about the source impedance of the device under test. If you use this method to calibrate your probe, the source impedance will be the impedance of the fixture used to connect the probe to the VNA. Almost invariably, this impedance will be 50Ω single-ended or 100Ω differential. This is a reasonable assumption for most real-world, high-bandwidth probing scenarios.

In practice, the difference between these two correction methods as far as the end user is concerned will be minimal if the probe impedance is much greater than the DUT's source impedance.

By David Maliniak Technical Marketing Communication Specialist Teledyne LeCroy

66


Modern electrical systems, such as heating and ventilation controls, boiler controls, manufacturing and process control equipment,

and railway signaling systems, usually have multiple inputs and outputs, and many internal connections with PLCs, contactors, switches, trips, and controls. Finding the cause of malfunctions with a conventional multi-meter is a tedious, time-consuming task, and possibly impossible, especially if the fault is intermittent. What these situations need is a device that can be left on- site to investigate such problems, logging and recording the electrical switch activity for as long as necessary. It should contain an internal battery for many days of use, and the recorded data should be viewable on a Windows PC with a search feature that enables the user to specify a particular combination of inputs to quickly locating fault incidents.

CONTROL SYSTEM FAULTSBy: Alan J Lowne, CEO Saelig Company Inc.

FINDING

77

TECH ARTICLE

Modern electrical systems, such as heating and ventilation controls, boiler controls, manufacturing and process control equipment,

and railway signaling systems, usually have multiple inputs and outputs, and many internal connections with PLCs, contactors, switches, trips, and controls. Finding the cause of malfunctions with a conventional multi-meter is a tedious, time-consuming task, and possibly impossible, especially if the fault is intermittent. What these situations need is a device that can be left on- site to investigate such problems, logging and recording the electrical switch activity for as long as necessary. It should contain an internal battery for many days of use, and the recorded data should be viewable on a Windows PC with a search feature that enables the user to specify a particular combination of inputs to quickly locating fault incidents.

CONTROL SYSTEM FAULTSBy: Alan J Lowne, CEO Saelig Company Inc.

FINDING

88













9

TECH ARTICLE

9












1010


Signals can even be monitored at a distance from the point of measurement, which makes observing difficult areas possible.

FTR-Birdie displays the on/off status of each input on bright LED indicators, and records precise time and date of each and every change on the inputs. It is designed for the rough real world and can be padlocked on-site for extended periods to monitor a suspect activity or intermittent faults. With its internal battery FTR-Birdie needs no external power, but can be connected to a PC for playback of the record in convenient display format for more detailed examination of the results.

FTR-Birdie records exactly what happened, when and in what order, so that faults can be traced quickly and easily. It can make huge savings in time and avoid unnecessary ‘swap-outs’. Its recording mode permits unattended operation and is ideal for intermittent faults. Signals can be monitored from outside control cubicles, with no need to work with the cubicle doors open.

Scenario 1 Solution: FTR-Birdie was connected to all the control signals, contactor signals, motor and pump power feeds to the FTR, switched on and left in logging mode. 3 days later, the fault happened again. The FTR was retrieved and the results replayed. All three days’ operation was available to look at. The events that were logged around 4.00

that morning showed that the signal from the auxiliary contacts on the pump contactor was missing. This prevented the main burner circuit starting, hence no heat. Obviously, the auxiliary contacts had become intermittent and the contactor needed to be replaced … problem solved. This single incident would certainly have more than paid for the cost of the FTR.

Scenario 2 Solution: An FTR was installed to monitor the various inputs and outputs and after 11 days, the problem occurred again. Studying the records showed that all the control systems were working properly, and the problem must be associated with the lifting motor.

This was exchanged and the problem was cured. Subsequent investigation showed that an intermittent poor connection was present on one of the field windings. The vibration of a second passing train would be enough to restore the connection, clearing the fault before it could be investigated.

Scenario 3 Solution: The FTR-Birdie, which accepts a wide range of input voltages, was connected to the machine, which ran at normal speed until the fault occurred. Logging these signals enabled the exact sequence of events that led up to the problem to be studied in detail. In particular, the order in which signals changed was analyzed, one step at a time.This showed that a momentary pulse from a proximity sensor was initiating an operation before its proper time. This occurred only when the machine was running at its normal speed due to centrifugal forces acting on a cantilevered mounting plate. Checking the operation of the sensor showed that its threshold adjustment had slipped. This gave an occasional false pulse only when the machine was running at full speed. A small trimpot adjustment and all was well. Each time the fault occurred, typically some thirty units would have to be manually reworked, at a cost of about $20 each. The FTR-Birdie repaid itself by saving just two occurrences of this problem!

Scenario 4 Solution: An FTR-birdie was connected so that the control signals to the thruster control rack and the power feeds to the thruster were monitored. After three weeks another glitch was reported. The FTR-Birdie recording showed that the problem was not with the thrusters or the local control rack, but in the signals coming down from the bridge. Subsequent investigation showed that interference from one of the radio transmitters

on the bridge and poor ground bonding had caused the false signals to be generated.

Scenario 5 Solution: Two FTR-Birdies were used to cover the whole requirement. Every week, the data was downloaded to a PC and, using the FTR software, converted to a text file for export to a standard Excel spreadsheet. It was then a simple matter to build the required analysis functions in the spreadsheet to provide the desired information.

ConclusionFTR-Birdie is a versatile tool for finding control systems faults quickly. It is a simple to use, self-contained electrical test and fault-finding logger which records and displays all on/off voltage changes at its 16 inputs. It is useful for solving expensive production-line-down situations in complex control systems, just like a ‘Black Box’ accident recorder. Application opportunities for the UK- patented FTR-Birdie include: buildings (HVAC systems, emergency power systems, elevators/escalators, alarms, lighting, security systems), transport (trucks, railcars, signaling, shipping, traffic control systems), industry (production machinery, process control, power systems, boiler rooms), automotive (service depots, R&D), and general science situations (experiments, R&D, datalogging, event logging, activity monitoring).

11

TECH ARTICLE

11

Signals can even be monitored at a distance from the point of measurement, which makes observing difficult areas possible.

FTR-Birdie displays the on/off status of each input on bright LED indicators, and records precise time and date of each and every change on the inputs. It is designed for the rough real world and can be padlocked on-site for extended periods to monitor a suspect activity or intermittent faults. With its internal battery FTR-Birdie needs no external power, but can be connected to a PC for playback of the record in convenient display format for more detailed examination of the results.

FTR-Birdie records exactly what happened, when and in what order, so that faults can be traced quickly and easily. It can make huge savings in time and avoid unnecessary ‘swap-outs’. Its recording mode permits unattended operation and is ideal for intermittent faults. Signals can be monitored from outside control cubicles, with no need to work with the cubicle doors open.

Scenario 1 Solution: FTR-Birdie was connected to all the control signals, contactor signals, motor and pump power feeds to the FTR, switched on and left in logging mode. 3 days later, the fault happened again. The FTR was retrieved and the results replayed. All three days’ operation was available to look at. The events that were logged around 4.00

that morning showed that the signal from the auxiliary contacts on the pump contactor was missing. This prevented the main burner circuit starting, hence no heat. Obviously, the auxiliary contacts had become intermittent and the contactor needed to be replaced … problem solved. This single incident would certainly have more than paid for the cost of the FTR.

Scenario 2 Solution: An FTR was installed to monitor the various inputs and outputs and after 11 days, the problem occurred again. Studying the records showed that all the control systems were working properly, and the problem must be associated with the lifting motor.

This was exchanged and the problem was cured. Subsequent investigation showed that an intermittent poor connection was present on one of the field windings. The vibration of a second passing train would be enough to restore the connection, clearing the fault before it could be investigated.

Scenario 3 Solution: The FTR-Birdie, which accepts a wide range of input voltages, was connected to the machine, which ran at normal speed until the fault occurred. Logging these signals enabled the exact sequence of events that led up to the problem to be studied in detail. In particular, the order in which signals changed was analyzed, one step at a time.This showed that a momentary pulse from a proximity sensor was initiating an operation before its proper time. This occurred only when the machine was running at its normal speed due to centrifugal forces acting on a cantilevered mounting plate. Checking the operation of the sensor showed that its threshold adjustment had slipped. This gave an occasional false pulse only when the machine was running at full speed. A small trimpot adjustment and all was well. Each time the fault occurred, typically some thirty units would have to be manually reworked, at a cost of about $20 each. The FTR-Birdie repaid itself by saving just two occurrences of this problem!

Scenario 4 Solution: An FTR-birdie was connected so that the control signals to the thruster control rack and the power feeds to the thruster were monitored. After three weeks another glitch was reported. The FTR-Birdie recording showed that the problem was not with the thrusters or the local control rack, but in the signals coming down from the bridge. Subsequent investigation showed that interference from one of the radio transmitters

on the bridge and poor ground bonding had caused the false signals to be generated.

Scenario 5 Solution: Two FTR-Birdies were used to cover the whole requirement. Every week, the data was downloaded to a PC and, using the FTR software, converted to a text file for export to a standard Excel spreadsheet. It was then a simple matter to build the required analysis functions in the spreadsheet to provide the desired information.

ConclusionFTR-Birdie is a versatile tool for finding control systems faults quickly. It is a simple to use, self-contained electrical test and fault-finding logger which records and displays all on/off voltage changes at its 16 inputs. It is useful for solving expensive production-line-down situations in complex control systems, just like a ‘Black Box’ accident recorder. Application opportunities for the UK- patented FTR-Birdie include: buildings (HVAC systems, emergency power systems, elevators/escalators, alarms, lighting, security systems), transport (trucks, railcars, signaling, shipping, traffic control systems), industry (production machinery, process control, power systems, boiler rooms), automotive (service depots, R&D), and general science situations (experiments, R&D, datalogging, event logging, activity monitoring).

15 Jonathan Drive, Unit 4, Brockton, MA 02301-5566Tel: (508) 580-1660; Fax: (508) 583-8989

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A DC Source used in many applications(Reference, Simulator, Stable Supply, Secondary Standard,. . .)

Call Today (508) 580-1660

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522 and Analogic Model 8200.

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http://bit.ly/1fMVGMU

1414


Good Measurement Practices Essential to Characterizing Charge Accurately

By Jonathan L. TuckerKeithley Instruments, Inc.

Part 3:Common Charge Measurement Applications

PART

3Charge Measurement Techniques

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TECH ARTICLE

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Part 3:Common Charge Measurement Applications

PART

3Charge Measurement Techniques

1616


Charge measurements include applications such as measuring capacitance and static charge on objects. Charge measurement techniques can also be used to measure very low currents (<10fA).

The coulombs function of an electrometer can be used with a step voltage source to measure capacitance. This technique is especially useful for testing cables and connectors because it can measure capacitances ranging from <10pF to hundreds of nanofarads. The unknown capacitance is connected in series with the electrometer input and the step voltage source. The calculation of the capacitance is based on this equation:

C = QV

Figure 1 illustrates the basic configuration for measuring capacitance with an electrometer with a built-in voltage source, such as Keithley’s Model 6517B Electrometer/High Resistance System (Figure 2). The instrument is used in the charge (or coulombs) mode and its internal voltage source provides the step voltage. Just before the voltage source is turned on, the meter’s zero check should be disabled and the charge reading suppressed by using the REL function to zero the display. Then, the voltage source is turned on and the charge reading noted immediately. The capacitance is calculated from:

C = Q2 – Q1 V1 – V1

where: Q2 = final charge Q1 = initial charge assumed to be zero V2 = step voltage V1 = initial voltage assumed to be zero

After the reading has been recorded, reset the voltage source to 0V to dissipate the charge from the device. Before handling the device, verify the capacitance has been discharged to a safe level. The unknown capacitance should be in a shielded test fixture. The shield is connected to the LO input terminal of the electrometer. The HI input terminal should be connected to the highest impedance terminal of the unknown capacitance. For example, when measuring the capacitance of a length of coaxial cable, connect the HI terminal of the electrometer to the center conductor of the cable, allowing the cable shield to minimize electrostatic interference to the measurement.

If the rate of charge is too great, the resulting measurement will be in error because the input stage becomes temporarily saturated. To limit the rate of charge transfer at the input of the electrometer, add a resistor in series between the voltage source and the capacitance. This is especially true for capacitance values >1nF. A typical series resistor would be 10kΩ to 1MΩ.

Figure 1.Capacitance measurement using a Keithley Model 6517B Electrometer/High Resistance System.

To read the second installment of the series, click the image to the left.

Figure 2. Model 6517B Electrometer/High Resistance System.


Unlike a voltage measurement, a charge measurement is a destructive process. In other words, making the measurement may remove the charge stored in the device under test. When measuring the charge on a device such as a capacitor, first disable the zero check of the electrometer, and then connect the capacitor to the high impedance input terminal. Zero check is a process where the input amplifier of the electrometer is reconfigured to shunt the input signal to low. Otherwise, some of the charge will be lost through the zero check impedance and won’t be measured by the electrometer. That’s because when zero check is enabled, the input resistance of the electrometer is about 10 mega-ohms. Opening the zero check switch produces a sudden change in charge reading known as “zero hop.” To eliminate the effects of zero hop, take a reading just after the zero check is disabled, then subtract this value from all subsequent readings. An easy way to do this is to enable the REL function after zero check is disabled, which nulls out the charge reading caused by the hop.

Charge Measurement Techniques

PART

2


The coulombs function of an electrometer can be used with a step voltage source to measure capacitance.

This technique is especially useful for

testing cables and connectors because

it can measure capacitances ranging

from <10pF to hundreds of nanofarads.

PART

3

http://issuu.com/eeweb/docs/modern_test___measure_-_rigol/5?e=0

17

TECH ARTICLE

17

Charge measurements include applications such as measuring capacitance and static charge on objects. Charge measurement techniques can also be used to measure very low currents (<10fA).

The coulombs function of an electrometer can be used with a step voltage source to measure capacitance. This technique is especially useful for testing cables and connectors because it can measure capacitances ranging from <10pF to hundreds of nanofarads. The unknown capacitance is connected in series with the electrometer input and the step voltage source. The calculation of the capacitance is based on this equation:

C = QV

Figure 1 illustrates the basic configuration for measuring capacitance with an electrometer with a built-in voltage source, such as Keithley’s Model 6517B Electrometer/High Resistance System (Figure 2). The instrument is used in the charge (or coulombs) mode and its internal voltage source provides the step voltage. Just before the voltage source is turned on, the meter’s zero check should be disabled and the charge reading suppressed by using the REL function to zero the display. Then, the voltage source is turned on and the charge reading noted immediately. The capacitance is calculated from:

C = Q2 – Q1 V1 – V1

where: Q2 = final charge Q1 = initial charge assumed to be zero V2 = step voltage V1 = initial voltage assumed to be zero

After the reading has been recorded, reset the voltage source to 0V to dissipate the charge from the device. Before handling the device, verify the capacitance has been discharged to a safe level. The unknown capacitance should be in a shielded test fixture. The shield is connected to the LO input terminal of the electrometer. The HI input terminal should be connected to the highest impedance terminal of the unknown capacitance. For example, when measuring the capacitance of a length of coaxial cable, connect the HI terminal of the electrometer to the center conductor of the cable, allowing the cable shield to minimize electrostatic interference to the measurement.

If the rate of charge is too great, the resulting measurement will be in error because the input stage becomes temporarily saturated. To limit the rate of charge transfer at the input of the electrometer, add a resistor in series between the voltage source and the capacitance. This is especially true for capacitance values >1nF. A typical series resistor would be 10kΩ to 1MΩ.

Figure 1.Capacitance measurement using a Keithley Model 6517B Electrometer/High Resistance System.

To read the second installment of the series, click the image to the left.

Figure 2. Model 6517B Electrometer/High Resistance System.


Unlike a voltage measurement, a charge measurement is a destructive process. In other words, making the measurement may remove the charge stored in the device under test. When measuring the charge on a device such as a capacitor, first disable the zero check of the electrometer, and then connect the capacitor to the high impedance input terminal. Zero check is a process where the input amplifier of the electrometer is reconfigured to shunt the input signal to low. Otherwise, some of the charge will be lost through the zero check impedance and won’t be measured by the electrometer. That’s because when zero check is enabled, the input resistance of the electrometer is about 10 mega-ohms. Opening the zero check switch produces a sudden change in charge reading known as “zero hop.” To eliminate the effects of zero hop, take a reading just after the zero check is disabled, then subtract this value from all subsequent readings. An easy way to do this is to enable the REL function after zero check is disabled, which nulls out the charge reading caused by the hop.

Charge Measurement Techniques

PART

2


The coulombs function of an electrometer can be used with a step voltage source to measure capacitance.

This technique is especially useful for

testing cables and connectors because

it can measure capacitances ranging

from <10pF to hundreds of nanofarads.

PART

3

1818






CONCLUSION









19

TECH ARTICLE

19





CONCLUSION









May–July 2014

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Figure 1:Signals at the same frequency created by a DDS generator (upper trace) and a Trueform generator (lower trace)

Figure 2:This 40 MHz sine wave from the 33600A shows less than 800 femto-seconds of jitter.

Figure 3:A DDS generator (upper trace) was unable to output all seven aberrations in this 2 MHz arbitrary waveform.

SPOTlighT


3

hiNTM E A S U R E M E N T

33

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5

Configure a low-cost, high-performance RF solution for wireless transceiver measurements by pairing a N9320B/N9322C spectrum analyzer with the N9310A RF signal generator using a 33500B/33600A Series waveform generator as its modulation input. You can measure any wireless connectivity device with ASK, FSK, or GFSK modulation across a range of industrial, automotive, and consumer electronics.


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6

Model Description

FeaturesMax reading

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Built-in PC interfaces

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7

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28







EVER-CHANGING DEMANDSInterview with David Graef - CTO of Teledyne LeCroy

COVER INTERVIEW

29






EVER-CHANGING DEMANDSInterview with David Graef - CTO of Teledyne LeCroy

30


Almost two years ago, Teledyne bought LeCroy. At the time, there were a number of benefits that were touted as to the synergies of both of these companies. Can you speak to that—how has the transition gone and what benefits have you seen arise as a result?

Teledyne has a very strong scientific group that does a lot of basic research. One of the main benefits of the merger is the indium phosphide process that Teledyne has. We have actually designed a high frequency probe amplifier to start to understand how this process works. We’ve been designing with IBM’s silicon germanium process for many years, so we took a relatively simple-designed probe amplifier and designed it into the indium phosphide process at Teledyne. We introduced a probe at DesignCon at the end of January that will be

released by the end of the year. That’s one of the synergies that they talked about and one that we’ve taken advantage of.

We are always pushing towards higher frequencies, and we’ve certainly done some work on how we use the indium phosphide to push the frequencies of real-time scopes. Our product line goes from very low frequencies like 40 MHz to now 100 GHz. These very high frequency scopes are based on a technology we call Digital Bandwidth Interleave, which uses a combination of time domain and frequency domain techniques. Fundamentally, it splits the input signals, translates one band

down into the bandwidth of the basic channel, and then reconstructs it with DSP. Anything above 36 GHz uses our DBI technology. The goal would be to have 4 channels at a larger bandwidth like 65GHz or more and that’s where the indium phosphide will help us.

Who do you see as the potential customer for that 100 GHz scope?

Very basically, there are two classes of customers who will use this. There are people doing optical research who need the real-time digitization of the optical field for complex optical modulation schemes to test their

reconstruction algorithms. The other vector is people doing basic research in any number of different fields where there are very fast pulses involved. A 3-½ picosecond wide pulse will be able to be resolved pretty easily. A sampling scope won’t be able to do that because it would have to be repetitive. These are single-shot events that are very fast and have very narrow pulse widths that people want to look at for various reasons.

Serial data standards are getting faster and faster. Arguably, you can’t send that kind of information any distance without some degradation. People still want to see the

“Over the years, people have moved away from just using the scope to

view the voltage vs. time waveforms and more

towards wanting to take actual, very detailed

measurements with the scopes.”

COVER INTERVIEW

31

Almost two years ago, Teledyne bought LeCroy. At the time, there were a number of benefits that were touted as to the synergies of both of these companies. Can you speak to that—how has the transition gone and what benefits have you seen arise as a result?

Teledyne has a very strong scientific group that does a lot of basic research. One of the main benefits of the merger is the indium phosphide process that Teledyne has. We have actually designed a high frequency probe amplifier to start to understand how this process works. We’ve been designing with IBM’s silicon germanium process for many years, so we took a relatively simple-designed probe amplifier and designed it into the indium phosphide process at Teledyne. We introduced a probe at DesignCon at the end of January that will be

released by the end of the year. That’s one of the synergies that they talked about and one that we’ve taken advantage of.

We are always pushing towards higher frequencies, and we’ve certainly done some work on how we use the indium phosphide to push the frequencies of real-time scopes. Our product line goes from very low frequencies like 40 MHz to now 100 GHz. These very high frequency scopes are based on a technology we call Digital Bandwidth Interleave, which uses a combination of time domain and frequency domain techniques. Fundamentally, it splits the input signals, translates one band

down into the bandwidth of the basic channel, and then reconstructs it with DSP. Anything above 36 GHz uses our DBI technology. The goal would be to have 4 channels at a larger bandwidth like 65GHz or more and that’s where the indium phosphide will help us.

Who do you see as the potential customer for that 100 GHz scope?

Very basically, there are two classes of customers who will use this. There are people doing optical research who need the real-time digitization of the optical field for complex optical modulation schemes to test their

reconstruction algorithms. The other vector is people doing basic research in any number of different fields where there are very fast pulses involved. A 3-½ picosecond wide pulse will be able to be resolved pretty easily. A sampling scope won’t be able to do that because it would have to be repetitive. These are single-shot events that are very fast and have very narrow pulse widths that people want to look at for various reasons.

Serial data standards are getting faster and faster. Arguably, you can’t send that kind of information any distance without some degradation. People still want to see the

“Over the years, people have moved away from just using the scope to

view the voltage vs. time waveforms and more

towards wanting to take actual, very detailed

measurements with the scopes.”

32


third or fifth harmonic of whatever they are transmitting—there are some purists out there who would want to see those kinds of results.

Could you talk about your HDO scopes and why there was a push for the additional 4 bits of precision?

Let me go back a little bit to give you some background. Walter LeCroy started the company back in 1964 making instruments for high-energy physics. Through the years, LeCroy was very good at designing high-speed electronics using discrete transistors, but we were also very good at taking lots of data and reducing the data down into some interesting information that a physicist running an experiment would be interested in seeing. For many years we were doing these kinds of translations in data. When Walter decided to introduce our first scope in 1985, we had, for the time, very long memory. If you look at our competitors who were making analog scopes, you’ll see that these scopes served primarily as a viewing tool. However, we approached it differently; we approached our scope as an analysis tool. As a result, we had longer memory, we had FFTs on scopes, and we had all sorts of capabilities that nowadays are very common in scopes. Over the years, people have moved away from just using the scope to view the voltage vs. time waveforms and more towards wanting to take actual, very detailed measurements with the scopes.

The customer has very high expectations for the accuracy and precision of the oscilloscope measurements that they make. This includes the very high frequency accuracy where no oscilloscope has specifications that people expect. By pushing the resolution to 12-bits, enhancing the accuracy and redesigning the signal conditioning chain to maintain that accuracy, we are trying to meet the very high expectations that our customers have. We are producing the highest quality, most accurate, precision measurements that people can get, because that’s the expectation. And we will continue to improve in those areas.

What are some of the current SI challenges in the industry today?

I think the biggest challenges are all the bad things that happen when you crank up the speed. Speeds are going up—everyone wants more and more data in all kinds of places almost instantaneously. All the things that happen and all the different effects

and how they can degrade the transmission of data from one place to another are all big challenges. Power supplies and power distribution networks become more and more important because there is a lot more focus on battery life and switching power modes in handheld devices. There can be very many power modes in handheld devices all to extend battery life. When you switch power modes and you have phase lock loops and delay lock loops doing their thing, you need to make sure that when you do that, things don’t come unlocked and that the circuitry still works properly.

We have a lot of tools in the scopes to be able to address these things. With our whole serial data analysis suite of tools, we can look at channels and look at crosstalk and cross-correlate between channels and know if there is something happening in one channel we can look in another channel to see if there is crosstalk. We can also de-embed fixtures or transmission channels. For example, if you are looking at a chip, and you want to see how it is going to operate over a backplane, you can just make measurements and stick in the S-parameters and see what will happen. The virtual probing capability allows you to define anywhere along the line where you’d like to be probing.

The HDOs for power supply design are pretty useful as well. People are looking at efficiencies on power supplies and noticing that they have gone up considerably. What might seem like a

relatively small perturbation in the rise time of the signal can actually be another 2 or 3% in the efficiency of a power supply. With the higher resolution, you can really see the details of the signal that you are looking at that you wouldn’t be able to see by averaging because some of them are not repetitive.

How do you make the instrument have high performance while still maintaining the ease of use?

It’s definitely a big challenge for us. There are really two vectors that we constantly target. One of them is signal integrity through the acquisition chain. That has to be as clean and pristine as possible—best signal to noise ratio, higher resolution, linearity, and accuracy. The other is by continually adding features to address new things that come up. For example, the optical field is using four-level signaling instead of simple, two-level binary. Complex modulations require some fancy acquisition and demodulation capability, which is something we are good at, but it’s a constant challenge to expose all that stuff without overwhelming the user. I think we’ve reached a level that we can present these complex tasks in an easy-to-use interface. But, of course, we continue to work on the UI, user experience and signal acquisition fidelity to provide the best, most accurate and most comprehensive measurement tools on the market so our customers can continue to rapidly innovate and bring their very cool products to the world.

“The virtual probing capability allows you to define anywhere along

the line where you’d like to be probing.”

COVER INTERVIEW

33

third or fifth harmonic of whatever they are transmitting—there are some purists out there who would want to see those kinds of results.

Could you talk about your HDO scopes and why there was a push for the additional 4 bits of precision?

Let me go back a little bit to give you some background. Walter LeCroy started the company back in 1964 making instruments for high-energy physics. Through the years, LeCroy was very good at designing high-speed electronics using discrete transistors, but we were also very good at taking lots of data and reducing the data down into some interesting information that a physicist running an experiment would be interested in seeing. For many years we were doing these kinds of translations in data. When Walter decided to introduce our first scope in 1985, we had, for the time, very long memory. If you look at our competitors who were making analog scopes, you’ll see that these scopes served primarily as a viewing tool. However, we approached it differently; we approached our scope as an analysis tool. As a result, we had longer memory, we had FFTs on scopes, and we had all sorts of capabilities that nowadays are very common in scopes. Over the years, people have moved away from just using the scope to view the voltage vs. time waveforms and more towards wanting to take actual, very detailed measurements with the scopes.

The customer has very high expectations for the accuracy and precision of the oscilloscope measurements that they make. This includes the very high frequency accuracy where no oscilloscope has specifications that people expect. By pushing the resolution to 12-bits, enhancing the accuracy and redesigning the signal conditioning chain to maintain that accuracy, we are trying to meet the very high expectations that our customers have. We are producing the highest quality, most accurate, precision measurements that people can get, because that’s the expectation. And we will continue to improve in those areas.

What are some of the current SI challenges in the industry today?

I think the biggest challenges are all the bad things that happen when you crank up the speed. Speeds are going up—everyone wants more and more data in all kinds of places almost instantaneously. All the things that happen and all the different effects

and how they can degrade the transmission of data from one place to another are all big challenges. Power supplies and power distribution networks become more and more important because there is a lot more focus on battery life and switching power modes in handheld devices. There can be very many power modes in handheld devices all to extend battery life. When you switch power modes and you have phase lock loops and delay lock loops doing their thing, you need to make sure that when you do that, things don’t come unlocked and that the circuitry still works properly.

We have a lot of tools in the scopes to be able to address these things. With our whole serial data analysis suite of tools, we can look at channels and look at crosstalk and cross-correlate between channels and know if there is something happening in one channel we can look in another channel to see if there is crosstalk. We can also de-embed fixtures or transmission channels. For example, if you are looking at a chip, and you want to see how it is going to operate over a backplane, you can just make measurements and stick in the S-parameters and see what will happen. The virtual probing capability allows you to define anywhere along the line where you’d like to be probing.

The HDOs for power supply design are pretty useful as well. People are looking at efficiencies on power supplies and noticing that they have gone up considerably. What might seem like a

relatively small perturbation in the rise time of the signal can actually be another 2 or 3% in the efficiency of a power supply. With the higher resolution, you can really see the details of the signal that you are looking at that you wouldn’t be able to see by averaging because some of them are not repetitive.

How do you make the instrument have high performance while still maintaining the ease of use?

It’s definitely a big challenge for us. There are really two vectors that we constantly target. One of them is signal integrity through the acquisition chain. That has to be as clean and pristine as possible—best signal to noise ratio, higher resolution, linearity, and accuracy. The other is by continually adding features to address new things that come up. For example, the optical field is using four-level signaling instead of simple, two-level binary. Complex modulations require some fancy acquisition and demodulation capability, which is something we are good at, but it’s a constant challenge to expose all that stuff without overwhelming the user. I think we’ve reached a level that we can present these complex tasks in an easy-to-use interface. But, of course, we continue to work on the UI, user experience and signal acquisition fidelity to provide the best, most accurate and most comprehensive measurement tools on the market so our customers can continue to rapidly innovate and bring their very cool products to the world.

“The virtual probing capability allows you to define anywhere along

the line where you’d like to be probing.”

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READY TO LAUNCH

For the launch of the Tiva C Series Connected LaunchPad, TI has partnered with Exosite, mentioned briefly above, to provide easy access to the LaunchPad from the Internet. The LaunchPad takes about 10 minutes to set up and you can immediately interact with it across the Internet and do things like turn an LED on and off remotely from the website and see the reported temperature as well. It can also display approximate geographic location based on the assigned IP address and display a map of all other connected LaunchPad owners if they are active and plugged-in to Exosite. “In addition, it supports a basic game by enabling someone to interface to the Connected LaunchPad through a serial port from a terminal while someone else is playing with them through their browser. It is basically showing how you can interact remotely with this product and a user even if you are across the globe,” Folkens explained.

START DEVELOPING

The Tiva C Series Connected LaunchPad is shipping now and the price is right; at $19.99 USD, it is less than half the price of other Ethernet-ready kits. The LaunchPad comes complete with quick start and user guides, and ample online support to ensure developers of all backgrounds are well equipped to begin creating cloud-based applications. “We have assembled an online support team to monitor the Engineering-to-Engineering (or E2E) Community,” Folkens said. “Along with this, you also got a free Code Composer Studio Integrated Development Environment, which allows developers to use the full capability. We also support other tool chains like Keil, IAR and Mentor Embedded.

Affordable, versatile, and easy to use, the Tiva Series Connected LaunchPad is well suited for a broad audience and promises to facilitate the expansion of ingenious IoT applications in the cloud. As Folkens concluded, “The target audiences actually are the hobbyists, students and professional engineers. A better way of looking at it is that we are targeting people with innovative ideas and trying to help them get those ideas launched into the cloud.”

http://bit.ly/jd6Wcw

3636


As embedded systems take on more sophisticated applications, they also require advanced external memory systems, such as DDR3, in order to offer adequate throughput. At times it can be very helpful to see memory activity and perform some level of memory analysis in order to properly validate and debug a prototype system. New options now allow this, and at very inexpensive price points compared to the recent past. New general-purpose, low cost logic analyzers offer the performance required for such measurements as well as related analysis tools to provide this kind of insight.

By Brad Frieden,

DDR3Low Cost

Decode & Analysis

37

TECH ARTICLE

37

As embedded systems take on more sophisticated applications, they also require advanced external memory systems, such as DDR3, in order to offer adequate throughput. At times it can be very helpful to see memory activity and perform some level of memory analysis in order to properly validate and debug a prototype system. New options now allow this, and at very inexpensive price points compared to the recent past. New general-purpose, low cost logic analyzers offer the performance required for such measurements as well as related analysis tools to provide this kind of insight.

By Brad Frieden,

DDR3Low Cost

Decode & Analysis

3838













39

TECH ARTICLE

39












4040


Performance analysis Although helpful, the typical deep-memory raw capture and related memory decoder output provide more information than can be easily evaluated manually by the logic analyzer user. But DDR performance tools provide useful analysis by taking all the captured and decoded information and processing it into a variety of performance-oriented views. Four examples of summary views include the Overview, Refresh Statistics, Address Histogram and Effective Data Rate as seen in Figure 3.

Figure 4. Memory compliance failure for four ACTIVATE windows (different banks) to be less than 45.0 ns

Expected memory cycle distributions can be verified with the “cycle distribution view” of the performance analysis tool during particular modes of target operation. It is easy to see if the target system is spending too much time in memory “Deselects”, for example.

A prototype might be working functionally but lack overall system throughput. A view of the Read and Write data rate can reveal a problem in the memory controller design. The overall efficiency factor can also indicate an issue. Here, a 51% efficiency rate, although not necessarily

bad, might not be adequate for the application. When it comes to using memory address space, the memory controller typically should spend very little time accessing a few memory locations and should spread those memory accesses over a range. The histogram view of the accessed memory space can reveal “hot spots” that can lead to premature memory failures.

Memory Compliance TestingAnother type of memory evaluation that can be helpful during prototype turn-on is a test of compliance to the JEDEC specification. This evaluation can expose errors within a memory controller design. Non-compliance to the spec can result in data errors. A DDR post process compliance tool is available that also works from Address and Command memory signals saved in logic

analyzer memory. The type of memory probe is selected along with the type of memory being evaluated, its data rate and the desired tests. With this information a suite of evaluation parameters can be tested using the compliance tool.

The results of such a test can be seen in Figure 4 where failures were discovered for the operation of four “Activates” occurring from different banks of memory.

By selecting the row which highlights an error, the interface displays the number of discovered errors for a particular operation compared to the total number of that operation. It also lists the exact state pairs associated with each error count in the deep memory trace. It is important not only to report that errors occur but to reveal the specific locations of those errors so that a root cause of failure can be pursued. A real-time compliance tool also triggers the logic analyzer on a violation.

Figure 3. DDR Performance Tool views of memory cycle distribution, Read/Write throughput, address access distribution, and effective data rate.

41

TECH ARTICLE

41

Performance analysis Although helpful, the typical deep-memory raw capture and related memory decoder output provide more information than can be easily evaluated manually by the logic analyzer user. But DDR performance tools provide useful analysis by taking all the captured and decoded information and processing it into a variety of performance-oriented views. Four examples of summary views include the Overview, Refresh Statistics, Address Histogram and Effective Data Rate as seen in Figure 3.

Figure 4. Memory compliance failure for four ACTIVATE windows (different banks) to be less than 45.0 ns

Expected memory cycle distributions can be verified with the “cycle distribution view” of the performance analysis tool during particular modes of target operation. It is easy to see if the target system is spending too much time in memory “Deselects”, for example.

A prototype might be working functionally but lack overall system throughput. A view of the Read and Write data rate can reveal a problem in the memory controller design. The overall efficiency factor can also indicate an issue. Here, a 51% efficiency rate, although not necessarily

bad, might not be adequate for the application. When it comes to using memory address space, the memory controller typically should spend very little time accessing a few memory locations and should spread those memory accesses over a range. The histogram view of the accessed memory space can reveal “hot spots” that can lead to premature memory failures.

Memory Compliance TestingAnother type of memory evaluation that can be helpful during prototype turn-on is a test of compliance to the JEDEC specification. This evaluation can expose errors within a memory controller design. Non-compliance to the spec can result in data errors. A DDR post process compliance tool is available that also works from Address and Command memory signals saved in logic

analyzer memory. The type of memory probe is selected along with the type of memory being evaluated, its data rate and the desired tests. With this information a suite of evaluation parameters can be tested using the compliance tool.

The results of such a test can be seen in Figure 4 where failures were discovered for the operation of four “Activates” occurring from different banks of memory.

By selecting the row which highlights an error, the interface displays the number of discovered errors for a particular operation compared to the total number of that operation. It also lists the exact state pairs associated with each error count in the deep memory trace. It is important not only to report that errors occur but to reveal the specific locations of those errors so that a root cause of failure can be pursued. A real-time compliance tool also triggers the logic analyzer on a violation.

Figure 3. DDR Performance Tool views of memory cycle distribution, Read/Write throughput, address access distribution, and effective data rate.

4242


PORTABLE LOGIC ANALYZER CAPABILITIESAddr/Cmd/Data ultra-fast, 256k samples timing capture (no decoder, no compliance and analysis toolset)

Yes, 12.5 GHz full channel (requires 68-channel model for x8 and x16 data width)

Addr/Cmd/Data deep timing capture on DDR3 (no decoder, no compliance and analysis toolset)

Yes, 5 GHz half channel for up to DDR3 1600 x8 or x16 (requires 102-channel model)

Addr/Cmd state capture on DDR3 Decoder, protocol compliance and analysis toolset

Yes, up to DDR3 1333 (667 MHz clock, cmd, addr, requires 34-channel model with option to increase max clock frequency to 700 MHz)

Addr/Cmd/Data state capture on DDR3/4 and LPDDR2/3 Decoder, Protocol Compliance and Analysis toolset

No, (cannot de-Mux addr/cmd bus on LPDDR2/3 or separate out Reads and Writes in state mode)

Timing mode capture of address, command and memory read and write data

Figure 5. 5 GHz timing

mode capture of DDR3 1333

address, command and data

Brad Frieden is a Product Planner/ Product Marketing Engineer for the Oscilloscopes and Protocol Division of Agilent and has been focused on general purpose logic analyzers and related applications. He has been with HP/Agilent for 30 years and has been involved in a variety of marketing roles in areas including fiber optic test, pulse generators, oscilloscopes, and logic analyzers. He received his BSEE from Texas Tech in 1981 and his MSEE from The University of Texas at Austin in 1991.

Figure 6. Portable logic analyzer capabilities for various memory measurements

A half-channel timing mode configuration is included with the analyzer for address, command and data capture. An example capture is shown in Figure 5.

A 102-channel model is necessary to provide 48 channels in the half-channel mode so that this measurement is able to capture address, command, and x8 or x16 data. Read and Write data is not separated in timing capture, but settled data bus Read and Write values would still be seen in the DATA row with an expanded time/division setting. If the state capture of separate Read and Write data is required, modular logic analyzer solutions are available that can accomplish this.

The measurements so far have all been state (synchronous) measurements but timing (asynchronous) measurements, including measurements on Read and Write data to track memory data flow,can also be useful. For the DDR3 1333 memory system being evaluated here, timing mode measurements require a timing sample rate that is fast enough to determine bus activity. A three-to-one ratio of logic analyzer sample rate-to-target system data rate is a good rule of thumb to follow.

For the 1333 data rate this would translate to a 4 GHz or faster timing rate. Low cost portable logic analyzers are available that have a half-channel, 5 GHz timing speed that meets this requirement.

SummaryIt is now possible to capture DDR3 1333 address and command signals with a low-cost, 34-channel general purpose portable logic analyzer in state (synchronous) mode as well as conduct memory decode, performance analysis, and compliance testing to help validate and debug digital designs. Further, by using the 5 GHz half-channel mode with a 102-channel analyzer, waveforms of DDR3 1333 address, command and data signals from a DRAM can be viewed to help with overall system evaluation. Although decode of the DDR3 traffic is not supported in Timing mode, valuable debugging insight is provided by viewing the timing waveforms. Modular analyzers are available for faster memories with higher data rates, including DDR4, LPDDR2/3, and LPDDR4 or for state capture with memory decode that separates Read and Write data on DDR3 1333 systems.

Specific logic analyzer requirements for particular memory applicationsTiming and state mode capabilities are summarized in Figure 6 including use of the DDR decoder and protocol compliance and analysis toolset.

43

TECH ARTICLE

43

PORTABLE LOGIC ANALYZER CAPABILITIESAddr/Cmd/Data ultra-fast, 256k samples timing capture (no decoder, no compliance and analysis toolset)

Yes, 12.5 GHz full channel (requires 68-channel model for x8 and x16 data width)

Addr/Cmd/Data deep timing capture on DDR3 (no decoder, no compliance and analysis toolset)

Yes, 5 GHz half channel for up to DDR3 1600 x8 or x16 (requires 102-channel model)

Addr/Cmd state capture on DDR3 Decoder, protocol compliance and analysis toolset

Yes, up to DDR3 1333 (667 MHz clock, cmd, addr, requires 34-channel model with option to increase max clock frequency to 700 MHz)

Addr/Cmd/Data state capture on DDR3/4 and LPDDR2/3 Decoder, Protocol Compliance and Analysis toolset

No, (cannot de-Mux addr/cmd bus on LPDDR2/3 or separate out Reads and Writes in state mode)

Timing mode capture of address, command and memory read and write data

Figure 5. 5 GHz timing

mode capture of DDR3 1333

address, command and data

Brad Frieden is a Product Planner/ Product Marketing Engineer for the Oscilloscopes and Protocol Division of Agilent and has been focused on general purpose logic analyzers and related applications. He has been with HP/Agilent for 30 years and has been involved in a variety of marketing roles in areas including fiber optic test, pulse generators, oscilloscopes, and logic analyzers. He received his BSEE from Texas Tech in 1981 and his MSEE from The University of Texas at Austin in 1991.

Figure 6. Portable logic analyzer capabilities for various memory measurements

A half-channel timing mode configuration is included with the analyzer for address, command and data capture. An example capture is shown in Figure 5.

A 102-channel model is necessary to provide 48 channels in the half-channel mode so that this measurement is able to capture address, command, and x8 or x16 data. Read and Write data is not separated in timing capture, but settled data bus Read and Write values would still be seen in the DATA row with an expanded time/division setting. If the state capture of separate Read and Write data is required, modular logic analyzer solutions are available that can accomplish this.

The measurements so far have all been state (synchronous) measurements but timing (asynchronous) measurements, including measurements on Read and Write data to track memory data flow,can also be useful. For the DDR3 1333 memory system being evaluated here, timing mode measurements require a timing sample rate that is fast enough to determine bus activity. A three-to-one ratio of logic analyzer sample rate-to-target system data rate is a good rule of thumb to follow.

For the 1333 data rate this would translate to a 4 GHz or faster timing rate. Low cost portable logic analyzers are available that have a half-channel, 5 GHz timing speed that meets this requirement.

SummaryIt is now possible to capture DDR3 1333 address and command signals with a low-cost, 34-channel general purpose portable logic analyzer in state (synchronous) mode as well as conduct memory decode, performance analysis, and compliance testing to help validate and debug digital designs. Further, by using the 5 GHz half-channel mode with a 102-channel analyzer, waveforms of DDR3 1333 address, command and data signals from a DRAM can be viewed to help with overall system evaluation. Although decode of the DDR3 traffic is not supported in Timing mode, valuable debugging insight is provided by viewing the timing waveforms. Modular analyzers are available for faster memories with higher data rates, including DDR4, LPDDR2/3, and LPDDR4 or for state capture with memory decode that separates Read and Write data on DDR3 1333 systems.

Specific logic analyzer requirements for particular memory applicationsTiming and state mode capabilities are summarized in Figure 6 including use of the DDR decoder and protocol compliance and analysis toolset.

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