•Volt-ohm-milliampere multimeter which can function

as a voltmeter, ohmmeter, or an ammeter

•works on the principle of d’ Arsonval meter

movement (Arsene d’ Arsonval, French Physicist)

>Permanent Magnet – provides a magnetic field that interacts with the moving

element

>Moving Element– activates a pointer when energized by the current being

measured

>Control Spring – provides the force for the pointer to return to its home

>Jeweled Bearing – ensures accuracy, supports the pivots on the moving

element shaft

>Coil – connected to the multimeter input so that current will flow through the

coil and deflect the pointer

>Full-scale meter current – the amount of current needed to deflect the

pointer all the way to the right of the scale

>NOTE:

*the meter used on the DC fundamentals circuit board requires 1 mA for full –

deflection

*when external circuits are added to the meter (for reading volts, amperes, or

ohms), meter current must be limited to 1 mA

*there is an internal resistance (RM) in the coil, for the meter in

DC fundamentals circuit board, RM is nominally 2300 ohms 20%

>learn the basic meter movement of an ammeter to measure

current

NOTE:

*meter must be placed in series with the circuit and must be

connected in proper polarity

*to use the same meter in applications where higher currents are

needed (extend the full-scale deflection), a shunt resistor must be

added in parallel

>use an ohmmeter to measure component or circuit resistance

without applying power to the circuit

>use an ohmmeter to check continuity and short or open circuit

>learn to calibrate an ohmeter

NOTE:

*ohmmeter measures resistance indirectly by measuring the

current that flows through a series circuit

*calibration and scale resistors are used to extend the range of

the ohmmeter

*calibration resistor is adjusted for a full-scale, zero-

ohms reading

>use a voltmeter to measure voltage

>extend the range of the voltmeter to measure multiple ranges of

voltages

NOTE:

*voltmeter measures voltage when a high resistance is placed in

series with the movement

*a multiplier or range resistor can extend the range of the

voltmeter

*voltage sensitivity is the result of the total resistance

divided by the full – scale deflection voltage (ohms / volt)

>fill-up the borrower’s slip with the following equipment in list:

>review the discussion materials

>follow the instructions in the procedures carefully

>provide the answers in the needed items within the procedure

(write your answers legibly and clearly, preferably in Engineering

Lettering)

>each Group must prepare a cover page, indicating the Title of the

Exercise, Group Number, and Name of each Member with

Signature

>duly accomplished Group reports must be submitted at the end

of the period / exercises

>Title Page

>Conclusions in each of the exercises

>Answers to Review Question for each exercise

>Answers to Unit Test

>Submission:

Feb 3, 2012 - Friday (C21)

Feb 4, 2012 - Saturday (B21)

>Group Report / Preliminary Report:

*Performance – 25%

*Data – 50%

*Presentation – 25%

>Individual Report / Final Report:

*Review Questions / Unit Test – 50%

*Conclusion – 20%

*Presentation – 30%

*NOTE: late reports will have corresponding deductions

from the total points of each report and failure to perform the

exercises will get 0% both for the Preliminary and Group

Report

Start with the exercises….