AVTECH ELECTROSYSTEMS AVRQ-4-B, Инструкция по эксплуатации

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VERIFICATION AND TROUBLESHOOTING
It is sometimes unclear whether the glitches observed on the opto-coupler output are
due to the opto-coupler or the test circuit.
To reduce the number of sources of possible interference or error, a daughterboard
scheme is used. This allows the drive conditions and the loading to be defined by
simple, compact circuits that are user-visible and user-changeable.
Similarly, the floating-side power or bias is derived from a simple battery circuit, whose
schematic is included in the schematics section of this manual. A more exotic switching
non-battery-based power supply design has been avoided, to minimize complexity. The
battery circuit is always active when a battery is installed, allowing current biases to be
measured while the DUT is installed in the daughterboard, but the daughterboard is
outside of the mainframe. For example, for current-drive devices with non-zero bias
levels, the current can typically be measured using compact DMM probes across
resistor R3.
Please note that A23 batteries have a limited mA·hr rating – typically 30 mA·hr
when operating at 15 mA – so the battery should be removed immediately after testing,
and its output should verified to be between 6V and 12V before each test.
The high-voltage circuits are only on when the instrument is powered on AND the DUT
door is closed AND the output has been set to the “on” state.
It is NOT possible to measure the drive current or voltage on the floating input side
while the high voltage pulse is active. It is dangerous, and it does not work anyway.
High-voltage differential probes DO NOT accurately reproduce signals if an
extremely fast high-voltage common mode signal is present. In order words, their CMTI
is worse than that of typical opto-couplers.
Using two probes and performing oscilloscope-based mathematics to calculate a
difference is NOT accurate enough to measure a ~1V differential signal in the presence
of a ~ 1.5 kV common mode signal.
If there is doubt about the stability of a non-zero drive signal, try soldering large
capacitances across the drive pins of the input to see if that stabilizes anything (taking
care to keep the capacitances away from the non-floating circuitry, for safety and
interference reasons). If there is no change, that would tend to eliminate the drive
signal as a source of problems.
If there is doubt about the stability of a zero-level drive signal, try soldering together the
two drive pins directly on the IC package (i.e., short them out), to see if that stabilizes
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