BK Precision 4011A Betriebsanleitung PDF herunterladen (Seite 21)

Laboratory 4: Instrument Characteristics

20109

resistance box in the circuit as shown. Adjust the resistance until the meter reads half of its

original value. The internal resistance of the ammeter is now equal to the value of the resis-

tance box. Measure and record this value of R

= R

when the I

new

= ½ I

old

Theoretical Question: (DO NOT TEST THIS EXPERIMENTALLY!) If R

were removed

and if the 10 kΩ resistor were replaced by zero ohms (0 Ω), what would be the current I?

2. Determine the effect of the ammeter’s internal resistance on the measurement of current.

WARNING: If you are not careful to turn off the voltage when changing the circuit below

(including switching values on the resistor boxes), you are likely to blow the fuse in the resis-

tor boxes or in the ammeter. Be sure that the resistor values are set as required before

turning on the power. Also note that the voltage for this step is only 2 volts.

a) 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 2.0 V output.

4) Turn “OUTPUT” OFF.

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

c) Set the resistance R

to 1 kΩ.

d) Set the Digital Multimeter to Amps, and the scale to 200 mAmps

e) Turn the power supply’s “OUTPUT” ON. Its output should be 2.0 volts.

f) Record the value of current indicated on the ammeter.

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

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BK Precision 4011A Betriebsanleitung Seite 21