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5700A/5720A Series II Calibrator
Service Manual
5-18
10 mV. A failure indicates the Differential Amplifier circuit on the Ohms Cal assembly
(A9) is probably at fault.
3309 A9: Diff Amp Gain Fault
The gain (nominal gain of 75) Differential Amplifier circuits on the Ohms Cal assembly
(A) is checked. The DAC output is set to 86.7 mV and connected to the -input of the Diff
Amp circuit with the +input connected to RCOM. The output of the Diff Amp circuit is
routed to the adc circuit on the DAC assembly, via the RCL line, where it is compared to
the 6.5V reference. This fault occurs if the determined gain is over 6% from the nominal
75. A failure indicates the Differential Amplifier circuit on the Ohms Cal assembly (A9)
is probably at fault.
3310 A9: Diff Amp Noise Fault
The noise of the differential amplifier circuit on the Ohms Cal assembly (A9) is checked.
The DAC output is set to 0V and connected to both the ±inputs of the differential
amplifier circuit. The output is routed to the adc circuit on the DAC assembly via the
RCL line. Ten readings are taken and this fault occurs if the difference between the
lowest and highest value if over 1 mV. A failure indicates the differential amplifier
circuit on the Ohms Cal assembly (A9) is probably at fault.
3311 A9/A10: Ohms 10:1 Divider Fault
The 2/5/10V SOURCE circuit is set for 10V and connected across the 100 kΩ resistance
in Z5 on the Ohms Cal assembly (A9). The resulting 1V across the 10 kΩ portion is
measure for 1V ±3% ±15 mV. A failure indicates the Ohms Cal assembly (A9) is
probably at fault.
3312 A9/A10: Ohms 1:1 Divider Fault
The 2/5/10V SOURCE circuit is set for 10V and connected across the 100 kΩ resistance
in Z5 on the Ohms Cal assembly (A9). This arrangement is measured for 10V ±3% ±15
mV. A failure indicates the Ohms Cal assembly (A9) is probably at fault.
3313 A9/A10: 10 Kilohm Diagnostic Fault
The 2/5/10V SOURCE circuit is set for 10V and connected across the 20 kΩ resistance
made from the 10 kΩ in Z5 on the Ohms Cal assembly, (A9) and the 10 kΩ string on the
Ohms Main assembly (A10) connected in series. The resulting 5V across the 10 kΩ
string on the Ohms Main assembly is measured for 5V ±3% ±15 mV. Measure the 5V
across the 10 kΩ string by connecting a DMM hi to TP2 and low to TP1 on the Ohms
Cal assembly (A9). If this voltage is greater than 5V the Ohms Main assembly (A10) is
probably at fault. If the voltage is less than or equal to 5V the Ohms Cal assembly (A9)
is probably at fault.
3314 A9/A10: 19 Kilohm Cal Diag Fault
The 2/5/10V SOURCE circuit is set for 10V and connected across the 29 kΩ resistance
made from the 10 kΩ in Z5 on the Ohms Cal assembly, (A9) and the 19 kΩ string on the
Ohms Main assembly (A10) connected in series. The resulting 6.55V across the 19kΩ
string on the Ohms Main assembly is measured for 6.55V ±3% ±15 mV. A failure
indicates the Ohms Main assembly (A10) is probably at fault.