Keithley 2182, User Manual, Page: 108 / 339

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 1k Ω and 10k Ω . The 1k Ω resistance is the result
of the parallel combination of the 2k Ω pot and the 2k Ω 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 1k Ω resistance component of the network, should be set to the 1V range
(1k Ω × 1mA = 1V) or autorange. Channel 2, which is used to measure the 10k Ω 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.
2k
Ω
Pot
HI
LO
CH 1
Model 220
Current Source
2k Ω
10k
Ω
2182
HI
LO
CH 2
DCV1
DCV2
1mA