Picotest M3500A Service Manual page 38

617 Ohms 100 uA source failed This test configures to the 1000V dc
range with the internal 10M 100:1 divider R204 connected across the input.
µ
The 100 A ohms current source is connected. The compliance limit of the
current source is measured. A 20ms ADC measurement is performed and
±
the result is checked against a limit of 0.12V 0.01V.
618 DC high voltage attenuator failed This test configures to the 1000 V
dc range. The 500nA ohms current source is connected to produce a nominal
5V signal. A 20ms ADC measurement is performed and the result is checked
±
against a limit of 5V 1V.
619 Ohms 1 mA source failed his test configures to the 1000V dc range
with the internal 10M 100:1 divider R204 connected across the input. The
1mA ohms current source is connected. The compliance limit of the current
source is measured. A 20ms ADC measurement is performed and the result
±
is checked against a limit of 0.12V 0.01V.
620 AC rms zero failed This test configures for the 100mV ac range with
the ac input grounded. The internal residual noise of the ac section is
measured and checked against a limit of -10mV to 70mV at the output of the
rms-to-dc converter.
621 AC rms full scale failed This test configures for the 100mV ac range.
The 1mA ohms current source is switched on to charge the ac input capacitor
C614. This produces a pulse on the output of the rms-to-dc converter which
is sampled 100ms after the current is applied. A 20ms A/D measurement is
performed and checked against a limit of 2V to 13V into the ADC.
622 10V reference failed This test configures to the 10V dc range with
the internal 5V. The result is checked against a limit of 4.55V ± 0.15V。
624 Unable to sense line frequency The supplied voltage AC2 is routed
through a comparator U4 to generate a logic input signal. This test checks
that the logic input from U4 to panel MCU U3 is toggling. If no logic input is
detected, the instrument will assume 50Hz line operation for all future
measurements.
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