Current Adjustment; Voltage Sourcecalibration - Keithley 595 Instruction Manual

8.511 Input Current Adjustment
Use the following procedure to null out any input currentY
present in the input stage. The inputs-current will then be
automatically temperature compensated to reduce the ef-
fects of high ambient temperature. Low input current is par-
ticularly important when making very low current measure-
ments. Proceed as follows:
1. Diiconn@t all input signals from the instrument. Place
the protection cap on the METER INPUT conn&tor.
2.. Removes the two screws securing the top cover and
remove it from the instrument.
NOTE
The proper warm up should be allowed. The top
cover must not be removed for more than five
minutes before adjustment.
3. Select the current function and place the instrument on
the 20 pA range. Select filter 3 and set delay time to
0.2sec
4. Enable ZERO CHECK and CORRect in that order.
5. Disable ZERO CHECK.
6. Wait several minutes until the displayed reading settles
down; about 2 counts (2fA) peal-to-peak noise is normal.
7. Locate the input current potentiometer R3l7 on the
preamp board (see Fi,we E-2). It is accessible through
a small hole in the shield.
8. Carefully adjust R317 for a reading of 0.000 12 counts
on the display. Repeated adjustment may be necessary.
Note: Remember to keep the top cover on the instrument
when not making internal adjustments.
85.12 Capacitance Offset Compensation
Perform the following~digital calibration procedure to com-
pensate for capacitance offset from the front panel. For front
panel calibration, skip step 4. For IEEE-488 bus calibration,
skip step 3.
1. Select the 200pF range, filter 3, 0.07 second delay and
O.OlV squarewave step. Disable ZERO CHECK if it is Oxi:.
2. Place the protection caption the METER INFUT connector.
3. For front panel calibration:
A. Make sure the ca&ration program is selected.
B. Press SHIFT and then the SELECT 7 button. The
display should settle to a reading of 00.00 pF i2
counts.
C.~ Press the ADJUST A or v button.
4. For IEEE-488 bus calibration, perform steps 1 and 2, and
then send J16X over the bus.
Compensation is now stored in temporary~memory. If its
is desired to store the calibration constants in permanent
memory at this time, perform the procedure in paragraph
6.5% Usually, it is most practical to complete the entire
calibration procedure before performing the storage pro-
cedure.
8.513 Voltage Source Calibration
Use the following procedure to-calibrate the voltage source.
Voltage source calibration can be performed at any time,
separate from meter calibration.
1. Connect the DMM to VOITAGE SOLACE OUTPUT as
&own in Figure 8-4.
2. Set the voltage source to output OO.OOV.
3. Turn on the voltage source output by selecting the DC~
WAVEFORM.
4. Place the DMM on the lowest DC voltage range possi-
ble without overranging &he instrument~and, verify an
output voltage of OV *lOmV.
5. Enable REL on the DMM to cancel the voltage offset.
6. Set~~the DMM to the 2OV (or similar) range and set the
voltage source to output 19.OOV
7. Adjust R166 (accessable from the rear panel - see Figure
8-2) for a DMM reading of l9.OOOV ilmV.
8. Set the voltage source to output OO.OOV, disable SUP-
PRESS, and connect the DMM to V ANALOG OUT-
PUT as shown in Figure 8-5.
9. Verify that the DMM reads OV &-2mV.
10. Enable REL on the DMM and set the voltage source to
xxtput lS.OOV, in that order.
11. Adjust R340 (see Figure 8-2) for a DMM reading of
1.9ooov *1oopv.
12. Turn off the voltage source output and disconnect the
DMM.