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The Q4610-00 also incorporates the function of the radiation indication/fault
detection card (6580500053/05334900) that had been supplied with earlier
generation systems. The function of this PCB is to enforce safety conditions based
on the expected status of the shutter and the signal level seen at the ash receiver.
The output of this portion of the circuitry provides the status of the red lamp, the
x-ray enable and if required a fault indication.
1. If the shutter is intended to be open and the receiver does not see an
adequate signal, the system interprets this as a potential safety violation. It
is conceivable the heads are split and the shutter is open.
2. In the opposite case if the chamber sees unexpected signal when the
shutter is intended to be closed. A fault will be issued and x-ray latch
disabled.
The decision is made based on the threshold signal, between 90mV and 180mV be
selecting a jumped in one of positions W1, W2, W3, or W4. No jumper maximizes
the threshold.
Jumper
Position
W1
W2
W3
W4
No Jumper
This card has a delay to account for the difference in time between a shutter open
command and the response seen in the ion chamber. By changing jumper position
from W10 to W7 the delay time can be changed in 1 seconds increments. The
shortest delay time (approximately 1 second) is set when jumper is in W10 position
and the longest delay time is achieved when there is no jumper.
Jumper
Position
No Jumper
W7
W8
W9
W10
Be aware that the MSS software also reacts to error scenario 1—when the MSS
recognizes that the signal level from the ion chamber is less than expected and
the shutter is commanded open, the MSS will immediately override and send a
close command to the system. The MSS typically reacts more quickly than the
termination board.
Approximate
Threshold Level
90mV
113mV
136mV
158mV
190mV
Approximate delay
(s)
5
4
3
2
1
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