BK Precision 4011A Betriebsanleitung PDF herunterladen (Seite 24)

Laboratory 4: Instrument Characteristics

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k) Calculate V

l) Calculate R

, the internal resistance of the voltmeter.

2. Determine the effect of the voltmeter’s internal resistance on the measurement of voltages.

WARNING: Be sure resistors are set as required before applying power to the circuit.

For this step of the experiment, do not adjust the voltmeter’s scale or the power supply’s

voltage adjustment at any time once measurements have begun.

a) Set Digital Multimeter to VOLTS and its scale to 20V. Set the AC/DC switch to DC.

b) With the DC power supply disconnected from any circuit:

1) Turn on the power supply.

2) Turn “OUTPUT” ON.

3) Adjust the power supply to provide 10.0 V output.

4) Turn “OUTPUT” OFF.

c) Connect the circuit shown below, using variable resistance boxes for the resistors.

d) Set the resistance R to 10 kΩ.

e) Switch the power supply’s “OUTPUT” to ON. Its output voltage should be 10.0 volts.

f) Record the voltage value indicated on the voltmeter.

g) Switch the power supply’s “OUTPUT” to OFF, without disturbing the voltage setting.

h) Set the resistance R to 500 kΩ.

i) Switch the power supply’s “OUTPUT” to ON.

j) Record the voltage value indicated on the voltmeter.

k) Switch the power supply’s “OUTPUT” to OFF.

l) Set the resistance R to 1 MΩ (or as close as you can get).

m) Switch the power supply’s “OUTPUT” to ON.

n) Record the voltage value indicated on the voltmeter.

o) Switch the power supply’s “OUTPUT” to OFF.

Analysis: Assuming that the internal resistance of the meter is infinite, calculate the theoreti-

cal values and compare these to your measured values. Explain any discrepancies and sum-

marize your understanding of the influence of the voltmeter on the measurements.

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BK Precision 4011A Betriebsanleitung Seite 24