Keithley SourceMeter 3A 2420, Руководство по обслуживанию

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1-4 Performance Verification
1
Ω
resistor characterization
The recommended 1
Ω
resistor should be characterized to ±300ppm or better before verifying
the 3A current measurement range. (You need not characterize the resistor if you are checking
only the 3A current source range.) Use the 4-wire ohms function of the DMM recommended in
Table 1-1 to measure the resistance value, and then use that measured value to calculate the cur-
rent during the 3A current measurement range test procedure.
Verification limits
The verification limits stated in this section have been calculated using only the Model 2420
one-year accuracy specifications, and they do not include test equipment uncertainty. If a par-
ticular measurement falls outside the allowable range, recalculate new limits based on Model
2420 specifications and corresponding test equipment specifications.
Example limits calculation
As an example of how verification limits are calculated, assume you are testing the 20V DC
output range using a 20V output value. Using the Model 2420 20V range one-year accuracy
specification of ±(0.02% of 2.4mV offset), the calculated output limits are:
Output limits = 20V ± [(20V
×
0.02%) + 2.4mV]
Output limits = 20V ± (0.004 + 0.0024)
Output limits = 20V ± 0.0064V
Output limits = 19.9936V to 20.0064V
Resistance limits calculation
When verifying the resistance measurement accuracy, it will probably be necessary to recal-
culate resistance limits based on the actual calibrator resistance values. You can calculate resis-
tance reading limits in the same manner described above, but be sure to use the actual calibrator
resistance values and the Model 2420 normal accuracy specifications for your calculations.
As an example, assume you are testing the 20k
Ω
range, and that the actual value of the nom-
inal 19k
Ω
calibrator resistor is 19.01k
Ω
. Using the Model 2420 20k
Ω
range one-year normal
accuracy specifications of ±(0.063% of reading + 3
Ω
), the recalculated reading limits are:
Reading limits = 19.01k
Ω
± [(19.01k
Ω ×
0.063%) + 3
Ω
]
Reading limits = 19.01k
Ω
±15
Ω
Reading limits = 18.9950k
Ω
to 19.0250k
Ω