325.6610.17 - 24 -
3.2.2.8 Watchdog Timer Circuit
The “watchdog” circuit is intended to let the operator know that the microprocessor has stopped
running. The circuit requires a constant input pulse from the microprocessor that only occurs
during proper operation. If the input pulses stop for more than a second, the watchdog circuit
will disable all of the relays and cause the display backlight to flash. In the event that this should
happen, restore normal operation by momentarily removing and re-applying AC power from
the unit thereby allowing the unit to cycle through its start-up procedure.
3.2.2.9 Self-Test
An optional self-test feature is available in the SETUP-CONFIGURE-INSTRUMENT-SELF TEST
menu item. This feature permits testing of the functional integrity of the receiver and some
of its electronics. This test causes the system to be checked for basic operation and proper
output. Once initiated, it operates automatically without further operator intervention (except
for the keypad test where user-action is required) as long as the appropriate data was entered
in the SETUP-CONFIGURE-INSTRUMENT-SELF TEST menu item.
The self-test sequence verifies that the unit is operating properly and is divided into two
sections:
• Standard - runs on all units
• Extended - requires entry of the Configuration Code (refer to section 3.2.2.9.2)
CAUTION
In SETUP, ALARMS, and DATA modes, gas-monitoring continues to
take place even though concentration values are not shown on the display.
However, when in SETUP, initiation of CALIBRATION, SELF-TEST or
SENSOR CHECK functions will temporarily suspend normal gas-monitoring.
3.2.2.9.1 Standard Tests
The standard test sequence that is performed on all units is as follows:
SELF-TEST
DISPLAY
SELF-TEST
KEYPAD
SELF-TEST
NVRAM
SELF-TEST
RAM
SELF-TEST
DIGITAL OUTPUTS
The test runs automatically once initiated, however, user-action is required as the keypad
self-test is performed. The user is prompted to press the appropriate keypad buttons
in the sequence from upper left to lower right on the keypad. The display will indicate
which button is to be pressed. Once the keypad self-test is completed, the test will
resume automatic operation.
3.2.2.9.2 Extended Tests
In order for extended tests to be run on optional instrument configurations, a
CONFIGURATION CODE must be entered. The CONFIGURATION CODE indicates
the receiver’s configuration. The CONFIGURATION CODE must be entered in the
SETUP-CONFIGURE-INSTRUMENT-ENTER CONFIG CODE menu item prior to
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