SRS Labs SR430, Manual

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Test and Calibration
criminated correctly. To check the trigger slope
and level, set the Records/Scan to 0 and press
[START]. Records will be triggered indefinitely.
Check the SYNC/BUSY output on a scope. This
signal only occurs after a trigger is recognized and
lasts only for the record acquisition and accumula-
tion time. Check that the TRIGD indicator on the
screen flashes for each trigger.
2)Incorrect discriminator levels or slopes. Verify
that the discriminator settings are correct. Use the
DISC output to check the discriminator output
pulses on an oscilloscope.
3)Signal inputs are overloaded. Check that the in-
puts are <±300 mV or, if the signal exceeds 300
mV, that the overloads do not last longer than 10
µs. If the overload lasts longer than 10 µs, the in-
put amplifiers will not recover for about 200 ns.
4)Incorrect bin width. Check that the bin width is
set correctly. A too narrow bin will result in smaller
data points, a too wide bin may overload before
expected.
5)The bin clock source is set to External. In this
case the EXT BIN CLK input controls the bin tim-
ing. If there is no input to the EXT BIN CLK, there
will be no bins.
6)Accumulation mode incorrect. Check that the ac-
cumulation is not toggling or externally controlled.
If accumulation is set to external, check that the
SUBTRACT input is receiving a valid TTL signal at
the correct time.
7)Accumulation is inhibited. If the INHIBIT input is
being driven, accumulation may be inhibited. In
this case, no records accumulate.
4th bin will have counts in it. This is because the
TEST pulses come every 20 ns. When the data
acquisition is DONE, every 4th bin should have
1000 counts in it. Once again, if the pulses are
landing on the bin boundaries, add a short length
of cable to delay the pulses. Also, adding cable
delay to the TEST cable can also move the pulses
into new bins. In this way, every bin can be tested
eventually.
Once these tests are completed, any bin width up
to 327 µs and any record length can be tested. Re-
member that the TEST pulses come every 20 ns
and that the first bin will always receive 1 less
count per trigger than the rest of the bins. Also, for
longer record times, the 1 kHz trigger rate will be
too fast and generate RATE errors. These may ei-
ther be ignored or the trigger rate lowered. Each
bin can only count up to 32767 in a single trigger
so bins wider than 327 µs will overload in a single
trigger. The wider the bin, the less accumulation is
allowed. Adjust the Records/Scan accordingly.
If problems are encountered, a scope should be
used to verify that SYNC/BUSY, BIN CLK OUT,
and DISC OUT are functioning properly. Set the
Records/Scan to 0 and start data acquisition.
Records will acquire without end allowing these
signals to be examined at length.
The SYNC/BUSY output is a TTL level signal
which goes high 45 ns after the trigger is received.
The signal goes low after the record is acquired
and accumulated. This time is equal to N x (bin
width + 250 ns) + 150 µs where N is the number of
records per bin. Terminate this output into a high
impedance.
The BIN CLK OUT is a NIM level 50Ω clock signal
which indicates the bin boundaries. Each transition
of the BIN CLK OUT is a bin boundary. The BIN
CLK is active only while during the record acquisi-
tion time (N x bin width). Terminate this signal into
5 0 Ω .
The DISC OUT is a NIM level 50Ω signal which in-
dicates that the discriminator has detected a
pulse. When using the TEST signal, the DISC
OUT should be a 50 MHz signal. Terminate this
signal into 50Ω.
If all signals check out and problems still exist,
contact the factory for more information.
COUNTING PROBLEMS
There are several reasons why the SR430 may
not seem to be counting correctly.
1)Bad triggering. The trigger input may not be dis-