Keithley SourceMeter 2425, Service Manual

Page: 34 / 141

Model 2425 Service Manual Performance Verification 1-19
2. Select the resistance calibrator external sense mode.
3. Configure the Model 2425 ohms function for the 4-wire sense mode as follows:
• Press CONFIG then MEAS
Ω
. The instrument will display the following:
CONFIG OHMS
SOURCE SENSE-MODE GUARD
©
• Select SENSE-MODE, then press ENTER. The following will be displayed:
SENSE-MODE
2-WIRE 4-WIRE
• Select 4-WIRE, then press ENTER.
• Press EXIT to return to normal display.
4. Press MEAS
Ω
to select the ohms measurement function, and make sure the source
output is turned on.
5. Verify ohms measurement accuracy for each of the resistance values listed in Table
1-7. For each measurement:
• Set the resistance calibrator output to the nominal resistance or closest available
value.
NOTE It may not be possible to set the resistance calibrator to the specified value. Use
the closest possible setting, and modify reading limits accordingly.
• Select the appropriate ohms measurement range with the RANGE keys.
• Verify that the Model 2425 resistance reading is within the limits given in the table.
6. Repeat the entire procedure using the rear panel INPUT/OUTPUT and 4-WIRE
SENSE jacks. Be sure to select the rear panel jacks with the front panel TERMI-
NALS key.
Table 1-7
Ohms measurement accuracy limits
Model 2425 range
Calibrator
resistance
1
Model 2425 resistance reading limits 2
(1 year, 18°C to 28°C)
2
Ω
20
Ω
200
Ω
2k
Ω
20k
Ω
200k
Ω
2M
Ω
20M
Ω
1.9
Ω
19
Ω
190
Ω
1.9k
Ω
19k
Ω
190k
Ω
1.9M
Ω
19M
Ω
1.89649 to 1.90351
Ω
18.9784 to 19.0216
Ω
189.824 to 190.176
Ω
1.89845 to 1.90155k
Ω
18.9850 to 19.0150k
Ω
189.847 to 190.153k
Ω
1.89861 to 1.90139M
Ω
18.9517 to 19.0483M
Ω
1
Nominal resistance values.
2
Reading limits based on Model 2425 normal accuracy specifications and nominal resistance values. If
actual resistance values differ from nominal values shown, recalculate reading limits using actual calibrator
resistance values and Model 2425 normal accuracy specifications. See Verification limits earlier in this
section for details.