Self-Test - Picotest M3500A Service Manual

All measurement control and bus command interpretation is performed in
the main controller (DSP) U1601, and the panel processor U3 and front-end
processor U2001 operate as slaves to the DSP. The main controller (DSP) is
a 16-bit fixed-point Digital Signal Processor. It has parallel and serial ports
to control various circuits, such as USB and COMM interface.
A conventional address/data bus is used to transfer data between the DSP
and the external RAM U1701 and flash memory. The flash memory is used to
store the firmware for M3500A operation and calibration data, and the
external RAM provides temporary operating storage.
The clock frequency of the DSP is controlled by an oscillating circuit consists
of a 10 MHz crystal.

3.5 Self-test

Self-test procedures are built in M3500A for checking that the logic and
measurement hardware are functioning properly. Every time when the
multimeter is powered on, a set of test procedures is performed to make
sure the basic function of the multimeter works properly. If any error occurs
during self-test procedures, it indicates that parts of the multimeter are not
operating properly and need to be serviced.
Warning! Erroneous self-test failures may occur if the setting of
power line voltage is incorrect. Errors may also occur because of signals
present on the input terminal (front and rear) during self-test procedure.
Long test leads can act as an antenna causing pick-up of ac signals.
Or users may execute a complete self-test by front panel operation. This test
procedure provides more tests for the hardware of M3500A than the
power-on tests. Please follow the procedure below to perform the complete
self-test.
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Procedure: MENU SYSTEM SELF TEST
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