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Operation
Operation
3
3-1
Section 3
Operation
3.1 Operation
Once installation is completed, operation is fully automatic. The 876A-1 Readout Module continuously
indicates the level of radioactivity measured at the detector site. When the radiation level exceeds an
alarm set point, an alarm is actuated.
The following steps explain how to operate the 875 monitor:
1. Turn the function switch to the TEST position, and press and release the Electronic Check Source
(ECS) push button. About four seconds later, the SAFE-RESET light should come on. Then press
and hold the CHANNEL TEST push button. The ALERT, HIGH, and CHANNEL TEST lamps should
light immediately.
When channel test is pressed, the high and alert
alarm relays are deactivated. (Their coils are de-
energized). The wiring of the channel test circuit is
such that the channel test lamp will not light unless
the alarm relay contacts are in the deactivated or
tripped state. This is for the purpose of assuring
that an actual contact state change has occurred,
identifying that the channel is in the test mode.
Reconciling these alarm conditions is the user's
responsibility, since the remote alarms are not
included in the standard containment monitor
system.
2. Release the CHANNEL TEST push button. The SAFE-RESET lamp should stay on. Either or both
of the HIGH (red) and ALERT (yellow) lamps may stay on or go out depending on the alarm reset
mode chosen by the installation of jumpers on the alarm circuit board. The monitor is supplied with
the manual reset mode selected.
3. To reset any alarm light, press the SAFE-RESET push button. If conditions are normal, the light will
go out.
4. Switch the function switch to the ALL position.
5. Again press the ECS push button. The panel meter indicator should go to a reading of about 10
3
R/h and the green SAFE-RESET light stays on in the operating condition. If the panel meter shows
little or no deflection at the pressing of the ECS push button, the green light should go out four
seconds after the ECS push button is pressed. In this case, follow troubleshooting procedures.
6. To set the alert and high alarm adjustments, remove two screws in the rear of the chassis, loosen
the knurled knob on the front of the chassis, and slide the module forward part way out of the rack
to reveal the adjustment potentiometers R513 and R509 on the relay driver printed circuit board. To
adjust the HIGH alarm, depress the red HIGH push button and adjust R513 (drawing 876A-1-75A)
until the meter indicates the desired alarm level. To adjust the ALERT alarm, depress the yellow
ALERT push button and adjust R509 (drawing 876A-1-75A) until the meter indicates the desired
NOTE