Agilent 34970A/34972A Data Acquisition / Switch Unit
Agilent 34970A/34972A Data Acquisition / Switch Unit
Agilent 34970A/34972A Data Acquisition / Switch Unit
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Chapter 6 Service<br />
Self-Test Procedures<br />
619 Ohms 1 mA source failed This test configures the 10 V range with the<br />
internal 1 0 M 100:1 divider A4U102 connected across the input. The 1<br />
mA current source is connected. A 20 ms ADC measurement is<br />
performed and the result is checked against a limit of 7 V ± 3.5 V.<br />
620 AC rms zero failed This test configures to the 100 mV AC range with<br />
the AC input grounded through A4K103. The internal residual noise of<br />
the AC section is measured and checked against a limit of –10 mV to 70<br />
mV at the output of the rms-to-dc converter.<br />
621 AC rms full scale failed This test configures for the 100 mV AC range.<br />
The 1 mA ohms current source is switched on the charge the AC input<br />
capacitor A4C301. This produces a pulse on the output of the rms-to-dc<br />
converter which is sampled 100 ms after the current is applied. A 20 ms<br />
A/D measurement is performed and checked against a limit of 10 V ± 8.5<br />
V into the ADC.<br />
622 Frequency counter failed This test configures for the 100 mV AC<br />
range. This test immediately follows test 621. With A4C301 holding<br />
charge from test 621 the AC input is now switched to ground through<br />
A4K103. This produces a positive pulse on the input to the frequency<br />
comparator A4U310. While C301 discharges, the ENAB FREQ bit is<br />
toggled four times to produce a frequency input to the counter logic in<br />
A1U205. A failure occurs if the counter can not measure the frequency<br />
input.<br />
4<br />
623 Cannot calibrate precharge This test configures to the 100 V DC<br />
range with no input. The ADC is configured for 200 ms measurements.<br />
The A1U205 pulse width modulated (PWM) DAC output (C224) is set to<br />
about 4 volts. A reading is taken in with A4U101 in the MC state. A<br />
second reading is taken in the PRE state. The precharge amplifier<br />
voltage offset is calculated. The A1U205 DAC output is set to about 1.5<br />
volts and the precharge offset is measured again. The gain of the offset<br />
adjustment is calculated. This test assures a precharge amplifier offset is<br />
achievable.<br />
6<br />
181
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