HP 3457A - Page 209

Test 8 checks the AC attenuator flatness on the 3V AC range. A 5V test signal is generated at A2U123
pin 13 and routed through A2U402 to the input of the A3 assembly. A measurement is made on the A3
assembly output signal and the Main Controller (A1U501) checks for convergence by checking to DAC
(A2U217) count limits of 512 +462. This limit assures being within the calibration range of the DAC.
Figure 8-10 illustrates some of the circuitry used for this test.
On error, if the AUXERR? command is executed, the number 256 will be displayed on the control panel
if their are no other errors (See Table 8-14). This indicates an AC attenuator flatness error that could
possibly be corrected by performing an internal mechanical adjustment on A3C332 and/or by perform-
ing the ACAL command. To adjust A3C332, execute DIAGNOSTIC 8 and adjust until the control
panel display indicates "PASSED" (refer to the AC Converter Frequency Response Adjustment in sec-
tion 5). If adjustment does not correct the error, executing DIAGNOSTIC 8 puts this test into a loop-
ing condition, This is useful while troubleshooting as signals can be monitored.
Test 9 checks the ohms precharge circuitry on assembly A2/1. The unit is set to the 300 volt DC range
with I power line cycle integration time and the latest auto calibration constant is sent to the A/D
Controller (A2U501) from the Main Controller (AI1U501). The input hybrid (A2U101) precharge
amplifier is selected by input hybrid switch PRE as the input to input amplifier QIIL and a zero
measurement is made. Next, a measurement is made through input hybrid switch MC. The difference
between the two readings is computed and the Main Controller performs error checking to limits of
512 +512 DAC counts. This limit assures being within the calibration range of the DAC. Figure 8-11 il-
lustrates some of the circuitry used for this test.
On error, if the AUXERR? command is executed, the number 512 is displayed on the control panel if
their are no other errors (See Table 8-14), This indicates an ohms precharge failure that could possibly
be corrected by performing the ACAL command,
8-78. Self Test Changes for New Main Controller (03457-66511)
Due to a new main controller board change, minor changes have been made to self test execution.
Auxiliary error codes 2048, 4096 and 8192 are no longer used. Designations for components used in the
description of self tests 0, | and 2 have changed. The sections that follow include an updated table of
error codes and an updated description of tests 0, 1, and 2.
8-79. Updated Power-on Self Tests
At instrument power-on, an abbreviated form of the complete Self Test procedure is executed to check
the fundamental digital hardware kernel and the communication link between the Main Controller
(ALLU601) and A/D Controller (A2U501). This consists of executing Self Tests 0, | and 2 in that order.
These 3 tests are discussed in detail in the following Self Test paragraphs.
Upon satisfactory completion of the power-on test routine, the instrument momentarily displays the
HP-IB address it is currently set to (the address is set to decimal 22 at the factory), emits a single "beep"
and sets itself to the predefined power-on state. The front panel indications of this state are; the DC
Voltage function, Auto-Range and automatic trigger are selected. For a complete list of power-on con-
ditions, refer to Section III, Table 3-1 in this manual.
HP 3457A Multimeter
8-44