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EMT 113/4 Sem II 2009/2010
The Basic Voltmeter Design
UNIVERSITI MALAYSIA PERLIS
FUNDAMENTAL OF ELECTRICAL ENGINEERING
EMT 113/4
EXPERIMENT 5
THE BASIC VOLTMETER DESIGN
MARKS
Results &
Calculation
22
Discussion
Conclusion
Total
%
10
5
37
100
NAME :
MATRIC NO. :
PROGRAMME :
DATE :
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
EMT 113/4 Sem II 2009/2010
The Basic Voltmeter Design
EXPERIMENT 6
BASIC VOLTMETER DESIGN
6.1
OBJECTIVES
To design and build a basic dc voltmeter within 5% accuracy as accepted to standard.
6.2
EQUIPMENTS
1 DC power supply
1 potentiometer, 20kΩ
1 panel meter, 0 – to 100mA
1 EVM or digital multimeter
Selected composition resistors, as required
6.3
INTRODUCTION
Voltmeters are one of the most frequently used pieces of test equipment in the
electronics industry. The basic dc voltmeter uses a current-sensitive meter movement
with the meter face calibrated in voltage units. A typical laboratory-quality voltmeter uses
a 50µA meter movement. For this meter movement to be used as a voltmeter, it is
necessary to put a resistor called a multiplier in series with the meter movement. Design
a voltmeter as described in procedure below.
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
EMT 113/4 Sem II 2009/2010
6.4
The Basic Voltmeter Design
PROCEDURE
1. Resistance measurement method
Connect your multimeter across the meter movement terminals to measure the
internal resistance. Record the value as Rm1
2. Potentiometer method
Figure 6.2: Potentiometer method
a. Connect the circuit as in Figure 6.2.
b. Set the 20 kΩ potentiometer to maximum and the voltage source to minimum.
c. Slowly increase the voltage to 1V.
d. Slowly decrease the resistance of the potentiometer until a full-scale reading
is obtained on the meter under test.
e. Calculate the internal resistance, Rm2, of the meter under test using the
millivolt and microampmeter readings. Record the results.
2. Calculate the average internal resistance of the meter under test as Rmave.
3. Construct the experimental circuit shown in Fig. 6.3. Use fixed composition resistors
for the multipliers.
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
EMT 113/4
The Basic Voltmeter Design
Figure 6.3: Experimental Circuit
4. Apply voltage according to the ranges to each range of the experimental circuit. Wait
until the needle stop to move. Observe the value of scale deflection as E2. Using the
ratio formula, calculate the absolute value for E2 and record in the table. E1 is the
expected value for full-scale deflection on meter movement. As example, for 5V
range, the full-scale deflection is 5V. Therefore, E1 = 5V.
5. Calculate and record the percent of error of each scale on your meter.
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
4
EMT 113/4
6.5
The Basic Voltmeter Design
RESULT
Your results should include:
i) meter movement data
ii) Voltmeter data
iii) Calculation of multipliers, E2 & percentage error
6.6
DISCUSSION
Your discussion should include:
i)
6.7
Explanations on your results.
CONCLUSION
Based on data, make your overall conclusion by referring to the objectives of this
experiment.
PUSAT PENGAJIAN KEJURUTERAAN MIKROELEKTRONIK
5