Verifying Dc Voltage - Keithley 2750 Service Manual

Model 2750 Multimeter/Switch System Service Manual

Verifying DC voltage

Check DC voltage accuracy by applying accurate voltages from the DC voltage calibrator
to the Model 7700 input terminals and verifying that the displayed readings fall within
specified limits.
CAUTION
Follow these steps to verify DC voltage accuracy:
1. Connect the Model 7700 CH1 H and L INPUT terminals to the DC voltage calibra-
tor as shown in
NOTE
Figure 1-9
Connections for Model 7700 DC volts verification
CH1
CH5 CH6
INPUT SENSE CH1 CH2 CH3 CH4
H L H L H L H L
H L H L H L H L
CH7
H L H L H L H L
CH17 CH18 CH19 CH20
H L H L H L H L H L H L H L H L
CH21 CH22 CH11 CH12 CH13 CH14 CH15 CH16
Model 7700
2. Install the Model 7700 in Slot 1 of the Model 2750, then turn on the power and
allow the unit to warm up for two hours before proceeding. Be sure the front panel
INPUTS switch is set to the REAR position.
3. Select the DC volts function by pressing the DCV key, and set the Model 2750 to
the 100mV range. Close Channel 1 by pressing the CLOSE key, then ENTER for
"SINGLE" channel, and then keying in 101.
4. Set the calibrator output to 0.00000mV DC, and allow the reading to settle.
5. Enable the Model 2750 REL mode. Leave REL enabled for the remainder of the
DC volts verification test.
6. Source positive and negative and full-scale voltages for each of the ranges listed in
Table
7. Press the OPEN key to open Channel 1.
Do not exceed 300V DC between the 7700 plug-in module INPUT H and
L terminals or between any adjacent channels.
Figure 1-9.
Use shielded, low-thermal connections when testing the 100mV and 1V ranges
to avoid errors caused by noise or thermal effects. Connect the shield to the cal-
ibrator's output LO terminal.
CH8 CH9 CH10
Output HI
INPUT
(V, 2 WIRE)
SENSE
(OHMS, 4 WIRE)
H L H L H L H L
1-10. For each voltage setting, be sure that the reading is within stated limits.
Performance Verification
Calibrator (Output DC Voltage)
Output
LO
Note: Use shielded, low-thermal cables
for 100mV and 1V ranges.
1-21