Rapiscan TSA TPM-903B Operation And Service Manual - page 26
TSA TPM903 Operations and Service Manual
Doc: # 5058 Rev. A
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4.2. MODES
4.2.1. SELF-TEST MODE
When the instrument is turned on, it performs a Power-On Self-Test (POST). The POST
performs the following tests:
RAM: Tests conventional memory, primarily the area used for the processor’s stack
NVRAM: Tests the battery-backed, non-volatile memory used to store parameters
LAMPS: The audio annunciator and both LEDs are turned on for approximately 4 seconds.
If any of these tests fails, the controller will display a "FAIL" message. The system cannot be put
into service until the problem is corrected.
After completing the POST, the system will enter the BACKGROUND mode and be ready to
operate after the initial 20-second background is obtained.
4.2.2. BACKGROUND MODE
BACKGROUND mode is the default mode for routine operation. The system will automatically
go to this mode after the initial self-test series. The display counts down from 19 to 0 during the
first background collection period. During this initial countdown, no other functions are
available, and occupancies are ignored. The unit then continuously takes 5-second background
counts and adds the most recent 4 together to display the most recent 20-second average (20-
second sliding background).
After the initial countdown, system status is displayed, and the system starts monitoring for
occupancy. The background display will update every five seconds to show the current
background being used for alarm calculations. While collecting background counts, the controller
compares the latest count with the high and low background alarm levels once a second. If the
background count is outside these limits, the unit will display DET X:LO/HI NNNN, where X is
the detector number, and NNNN is the current background for that detector.