C.K. PITHAWALA COLLEGE OF ENGINEERING AND TECNOLOGY

Branch ElectricalSubject ELECTRICAL EASUREMENT&

MEASURING INSTRUMENTGroup No. 14Topic Display method and Devices,

Different type of Recorder, Galvanometric recorders, Pen driving system.

ENROLLMENT NO.

NAME OF STUDENTS

160093109005 JAMBUKIYA HARDIK B.

160093109009 KULKARNI BHAVIKKUMAR H.

160093109014 PATEL RAHULKUMAR B.

160093109017 SAILOR HIRENKUMAR A.

160093109018 SALUNKHE HITESH S.

DISPLAY METHODS AND DEVICES

•  Data analysis is the important parameter of any study for which the data generated by any device should be displayed / recorded successfully.•  The instrumentation plays an important role in these

studies.•  This data presentation can be categories into two

groups such as indicators and recorders.•   Indicating instruments indicates the instantaneous

data of the quantity under measurement and recording type of instruments provides graphical representation of the quantity under measurement on screen or on graph paper.•  The major advantage of recording type of

instrumentation system is that the previous nature of the quantity can be easily analyzed in this system.

DIFFERENT TYPES OF RECORDERS

• Electronic recorders are classified in two following ways :• 1.Analog recorders and 2.Digital recorders• Further analog recorders are classified as : a)Magnetic tape recorders b)Graphic recorders c) Oscillographic recorders• Digital recorders are classified as : a)Synchronous digital recorders b)Incremental digital recorders• Analog recorders the input signal (quantity under

measurement) is translated into some position on a chart and a pen marks the point on the chart.• Either pen or the chart is moved with the time and

continuous graph is plotted on the chart against the time scale.

GALVANOMETRIC RECORDERS

•  The working principle is same as that of the moving coil instruments which is already explained earlier in the book.•  In conventional moving coil instruments the

controlling torque is produced by the spiral springs but in case of galvanometric recorders the controlling torque is produced by the current flowing through the suspension of the coil.•  A pointer is attached to the suspension with a pen at

its end. As the coil moves as per the deflecting torque produced by the quantity under measurement an ink trace is produced on the chart.

From Fig. R = length of pointer• Ф= angular deflection of the coil• y = displacement of the pen

FIG. CURVILINEAR PAPER

Then displacement of the pen (y) is given as• y = R sin Ф• The relationship between current and

displacement is non-linear since the angle Ф is proportional to the current through the coil.

FIG. KNIFE EDGE RECORDER

• The error due to non-linearity can be limited to 0.5 % if the angular displacement is restricted to ±10º.• The curvilinear paper is used for the recording since the pen

draws curve instead of a straight line.• Fig. shows the curvilinear paper used in the galvanometric

recorders.                            • But it suffers for the drawback that there are difficulties in

interpolation for points between the curved lines.•  To overcome this difficulty rectilinear charts are used rather

than curvilinear charts which are also known as knife edge recorder.• It consists of heat sensitive paper which is impregnated with a

chemical that shows a marked colour when heated with the contact with stylus.• Use of knife edge recorder eliminates the curve tracing but non-

linear ship between displacement y and angle Ф still exists.

PEN DRIVE RECORDER

• A PEN DRIVE RECORDER IS AN ELECTROMECHANICAL INSTRUMENT THAT RECORDER AN ELECTRICAL OR MECHANICAL INPUT TREND ONTO THE CHART.• IT MAY CONTAIN NUMBER OF INPUT AND TO DRAW

SUCH QUANTITIES COLOURED PENS ARE USED.• CHART RECORDER MAY BE ENTIRELY MECHANICAL

WITH CLOCKWORK MECHANISM FOR DRIVING CHART.• PEN DRIVING RECODERS ARE FOUND IN BASIC THREE

TYPES • STRIP CHART RECORDERS• CIRCULAR CHART RECORDERS• ROLL CHART RECORDERS

WHAT IS A DATA/CHART RECORDER?

A data/chart recorder is an electronic instrument that keeps track of various measurements required in industrial and laboratory environments. Broadly speaking, it is used to record: oprocess measurements for such variables as temperature,

pressure, flow, pH, and humidity - scientific and engineering data for applications such as testing and diagnostics, statistical analysis, and other laboratory work that requires a graphic or digital record of variables

oThere are scores of data recorder models on the market, ranging from $100 standalone chart recorders that use paper and a pen to measure a single input, such as temperature, to $4000- plus high-speed models that accept 30 inputs. These, however, are the extremes—gone are the days when most data recorders could be classified as either simple, midrange, or complex. In recent years, for example, conventional analog chart recorders have hybridized with data loggers, and PC-based functions have been added to most of the product categories outlined below.

STRIP CHART RECORDERS

• Strip chart recorders consist of a roll or strip of paper that passes linearly beneath one or more pens. As the signal changes, each pen’s deflection records the process being measured in the form of a chart. Well suited to recording of continuous processes, strip chart recorders are commonly used in both laboratory and process-measurement applications. For future reference, sections of the paper can be torn off and archived.

CIRCULAR CHART RECORDERS

• A circular chart recorder records data on a paper disc rotated beneath one or more pens, which, as in a strip chart recorder, deflect with fluctuating electrical signals. The difference is that the resulting chart is circular rather than linear. Circular chart recorders are ideal for batch processes that operate within a known timeframe. They can be configured so that each rotation of the chart covers a standard time period—1 hour, 24 hours, 7 days, etc. Some recorders will also accommodate non-standard periods. The advantage of a circular chart is that, at a glance, it gives a complete history of one or several variables over the specified period.

ROLL CHART RECORDERS

• Roll chart recorder are similar to strip chart recorders except that the recorder data is stored on a round roll, and the unit is usually fully enclosed.• The pen drive recording system is driving a pen at a

steady rate by a clockwork or electrical drive mechanism.• Generally a miniature synchronous motor is used for

this purpose. This motor run at a constant speed at power frequency.

MAGNETIC RECORDER

• Method of preserving sounds, pictures, and data in the form of electrical signals through the selective magnetization of portions of a magnetic material. The principle of magnetic recording was first demonstrated by the Danish engineer Valdemar Poulsen in 1900, when he introduced a machine called the telegraphone that recorded speech magnetically on steel wire.

• In the years following Poulsen’s invention, devices using a wide variety of magnetic recording mediums have been developed by researchers in Germany, Great Britain, and the United States. Principal among them are magnetic tape and disk recorders, which are used not only to reproduce audio and video signals but also to store computer data and measurements from instruments employed in scientific and medical research. Other significant magnetic recording devices include magnetic drum, core, and bubble units designed specifically to provide auxiliary data storage for computer systems.

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