VI-700 V&l Source
14
Chapter 7
CALIBRATION
CALIBRATION
The VI-700 should be calibrated every twelve months
or more frequently if inaccurate outputs are sus-
pected.
7.1
Equipment Required
1. Precision digital dc voltmeter, 4-1/2 digit,
with 0.2 V, 2 V, and 20 V full scale ranges,
accurate to better than 0.01%.
2. Precision digital dc ammeter, 4-1/2 digit, with
0.2 mA, 2 mA, and 20 mA full scale ranges,
accurate to better than 0.01%.
7.2
Disassembly Procedure
WARNING
HIGH VOLTAGES EXIST WITHIN THIS
INSTRUMENT.
REFER SERVICING AND CALIBRATION TO
QUALIFIED PERSONNEL.
OBSERVE ALL APPLICABLE SAFETY PRE-
CAUTIONS.
OBSERVE ALL ESD PRECAUTIONS.
Remove the four screws on the bottom of the unit
that are inside the feet. Carefully lift off the top cover.
All calibration steps are performed on the printed cir-
cuit board. Refer to Figure 5.1 for the locations of
the various test points and trimmer potentiometers.
In the instructions to follow, the notation “A” refers
to an integrated circuit (IC), and an appended num-
ber refers to a particular pin on that IC, e.g. 1-A5/2
refers to pin 2 of IC 5 on the main printed circuit
board. The notation “T” refers to a trimmer potenti-
ometer.
7.3
Calibration Steps
Turn on the VI-700 and allow it to stabilize for one
hour.
7.3.1 Voltage Calibration
1.
Attach the digital voltmeter (DVM) leads se-
curely to the voltage output binding posts.
2. Set the VI-700 to 0.000 on the X0.l range.
3. Adjust trimmer 1-T4 to obtain a voltage as
close to zero as possible. 50
µ
V or less is
satisfactory.
4. Set the VI-700 to 1.799 on the X10 range.
5.
Adjust trimmer 1-Tl to obtain a voltage of
17.990 V.
6. Set the VI-700 to 1.799 on the Xl range.
7. Adjust trimmer 1-T3 to obtain a voltage of
1.7990 V.
8. Set the VI-700 to 1.799 on the X0.1 range.
9. Adjust trimmer 1-T5 to obtain a voltage of
179.90 mV.
7.3.2 HV (X10) Output - Optional
The X10 output is calibrated as follows:
1. Set the front panel output to 19.99 V.
2. Monitor the rear panel output.
3. Locate the potentiometer in the center of the
PC board attached to the roof of the unit.
4. Adjust the potentiometer until the X10
output voltage is 199.9 V.
