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power. The *C0=<value><EOS>, *C1=<value> <EOS>, and
*C4=<value><EOS> commands can be used to set the values of the CAL0,
CAL100, and CAL400 parameters respectively.
8.2 Calibration Procedure
Calibration requires four-wire 100Ω and 400Ω resistors of 6.25 ppm uncer
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tainty and a 0Ω resistor (or short). For verification, 25Ω and 200Ω resistors of
10 ppm accuracy are also required. The resistors are connected to the input the
same way probes are. The calibration procedure is as follows:
1.
Connect a 0Ω resistor to the input and measure its resistance. Note the
average error in the measurement. Adjust the CAL0 parameter by sub
-
tracting the measured error. For example, if the input is exactly 0.0000Ω
and readout shows –0.0011Ω, the CAL0 parameter should be adjusted
by adding 0.0011 to it.
2.
Connect a 100Ω resistor to the input and measure its resistance. Note the
average error in the measurement. Adjust the CAL100 parameter by sub-
tracting the measured error. For example, if the input is exactly
100.000Ω and the readout shows 100.029Ω, the CAL100 parameter
should be adjusted by subtracting 0.029 from it.
3.
Connect a 400Ω resistor to the input and measure its resistance. Note the
average error in the measurement. Adjust the CAL400 parameter by sub-
tracting the measured error. For example, if the input is exactly
400.000Ω and the readout shows 399.991Ω, the CAL400 parameter
should be adjusted by adding 0.009 to it.
4.
Verify the accuracy at 0Ω, 25Ω , 100Ω, 200Ω, and 400Ω. The accuracy
should be within the short-term accuracy limits given in the
specifications.
1502A Thermometer Readout
User’s Guide
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