User manual

5-18 Ratio and Delta
Applications
Calibrating resistor network dividers
Ratio can be used to calibrate resistor network dividers. The 1:10 divider network in
Figure 5-5 is made up of nominal resistances of 1kΩ and 10kΩ. The 1kΩ resistance is the result
of the parallel combination of the 2kΩ pot and the 2kΩ resistor. The pot provides fine tuning of
the network.
Figure 5-5
Calibrating 1:10 divider
The Keithley Model 220 is used to source a constant current of 1mA. Channel 1, which is
used to measure the 1kΩ resistance component of the network, should be set to the 1V range
(1kΩ × 1mA = 1V) or autorange. Channel 2, which is used to measure the 10kΩ resistance
component, should be set to the 10V range (or autorange).
When Ratio is enabled, the Model 2182 will display the result of V1 (≈1V) divided by V2
(≈10V):
Filt V1 ≈1V
Ratio = = = ≈0.1
Filt V2
≈10V
The above calculation includes Channel 1 Filter. If Filter is not
used, remove the “Filt” component from the calculation.
The network can then be calibrated by adjusting the network pot until a reading of 0.10000
is displayed.
2kΩ
Pot
HI
LO
CH 1
Model 220
Current Source
2kΩ
10kΩ
2182
HI
LO
CH 2
DCV1
DCV2
1mA