Keithley 177 Instruction Manual page 36

Table 5-8. DC Attenuation end Chopper Amplifier Checks
Step
1
ltemlComponent
Required Condition
Turn on power. Select 20mVDC
range. Short input end adjust
F.P. Zero for + .OOOO on display.
2 TP5. TP6"
=-7.5V DC (on DMM).
3
4
External voltage
source.
RI43 (yellow wire
slide)".
Apply + 19mV. Calibrated input.
+ 19mV.
5
6
7
8
9
10
11
12
13
14
15
16
TPl*
+ 1.9v
External voltage
Select 200mVDC range. Apply.
source.
+ 190mV.
RI43 + 190mV
TPl
+1.9v
External voltage
Select 2VDC range. Apply
source.
+ 1.9v.
R143, TPl +1.9v
External voltage
Select 20VDC range. Apply
source.
+ 19v.
R143
+1.9v
External voltage
Select 200VDC range. Apply
source.
+ 19ov.
R143
+1.9v
I
External voltage Select 1OOOV (12OOVI DC
source.
range. Apply + IOOOV.
RI43 +1v
*On maln pnnted circuit board, see Figure 5-l.
Remarks
NOTE: Insufficient zero
adjustment may indicated
leaky FET switches in
Chopper Amplifier Circuit.
Chopper Drive. Signals are
actually 0 to -15 square
waves et 390Hz. A steady
zero volt or -15V signal
indicates a problem in the
chopper drive or clock
circuitry.
Input to chopper amplifier
+ 1 attenuation (range
resistors).
Input to U106, chopper
output ( x 100 gain).
Calibrated input,
Input to chopper amplifier
+ 1 attenuation.
Input to U106, chopper
output t x 10 gain).
Calibrated input.
+ 1 attenuation, x 1 chop-
per gain.
Calibrated input.
f 10 attenuation (range
resistors).
Calibrated input.
f 100 attenuation (range
resistors).
Calibrated input.
+ 1000 attenuation (range
resistors).
5-10