Resistance Measurement Accuracy - Keithley SourceMeter 3A 2420 Service Manual

Resistance measurement accuracy

Use the following steps to verify that Model 2420 resistance measurement accuracy is
within specified limits. This procedure involves applying accurate resistances from a resis-
tance calibrator and then verifying that Model 2420 resistance measurements are within re-
quired limits.
CAUTION
1.
Figure 1-4
Connections for resistance
accuracy verification
Before testing the 2Ω and 20Ω ranges make sure your resistance calibrator
can safely handle the default test currents for those ranges (see Model 2420
and calibrator specifications). If not, use the CONFIG OHMS menu to select
the MANUAL source mode, then set the source current to an appropriate safe
value. When using the manual source mode, total resistance reading uncer-
tainty includes both Source I and Measure V uncertainty (see specifications),
and calculated reading limits should take the additional uncertainty into ac-
count.
If using the Fluke 5450A resistance calibrator, you cannot use the Auto Ohms
mode of the Model 2420 to verify the 2Ω range. The 1A test current for the 2Ω
range of the Model 2420 will damage the calibrator. On the Model 2420, use
the CONFIG OHMS menu to select the MANUAL source mode, and then set
the source (test) current to 100mA.
With the power off, connect the resistance calibrator to the Model 2420 INPUT/OUT-
PUT and 4-WIRE SENSE jacks, as shown in Figure 1-4. Be sure to use the 4-wire con-
nections as shown.
EDIT V I
DISPLAY
0 1
TOGGLE
LOCAL REL
POWER
6 7
DIGITS SPEED
Resistance Calibrator
4- WIRE INPUT/
SENSE OUTPUT
HI
75V 5V 75V
PEAK PEAK PEAK

2420 3A SourceMeter
LO
250V
MEAS SOURCE
PEAK
Ω
FCTN V I
RANGE
2 3 4 5 EDIT
AUTO
TERMINALS
FILTER LIMIT TRIG SWEEP
RANGE ON/OFF FRONT/
8 9 +/-
REAR
STORE RECALL CONFIG MENU EXIT ENTER
OUTPUT
Model 2420
Output HI
Output LO
Performance Verification
Sense HI
Sense LO
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