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Document: LT0273 MX4428 MXP Engineering / Technical Manual
Device Processing
Issue 1.5 24 March 2006 Page 9-15
9.13 FILTER STEP LIMITS
Note that Step Limits are always expressed as “Units per 5 seconds”. This differs from MPR
where heat units are “units per 10 seconds”, but smoke limits are “time to alarm” (the
inverse). The MXP change results in
• Heat and smoke being consistent with each other.
• Using a constant slope, rather than a constant time to alarm, as the threshold is varied,
means that increasing the alarm threshold also means that the minimum time to alarm
will be increased which is generally what would be expected. This gave better results
with the various sensitivities of the photo detector in the SSL test room, i.e. a constant
Step Limit could be used for all sensitivities.
9.14 ZONE ALARM TEST
A zone alarm test performs a test in the detector for all detectors in a zone which are
capable of supporting it viz 814PH, 814CH, and 814I. The Detector LEDs do not operate. No
filtering is applied during remote tests and the fuzzy logic is replaced by a simple comparison
test. Any devices already in alarm, prealarm or fault, or isolated, do not partake in the test.
Failure of a capable detector to produce the expected output generates an immediate fault.
The actual alarm returned to the MX4428 goes through AVF if programmed.
The MXP does not return “Test Pass” until all alarm-capable devices in the circuit go into
alarm.
9.15 ZONE FAULT TEST
No MX detectors are capable of a remote fault test. Therefore with all detectors and devices
a fault is simulated in polling software.
“Test Pass” requires all devices in the circuit to pass.
9.16 AUTOTEST AND SYSTEM TEST
The Flash Checksum is checked. (Note also, a checksum fail on power up will result in the
MXP application software not even starting, but the MXP will await a program load via its
diagnostic port.)
Specific checking of the configuration RAM is not required as it is being continually checked
(with anomalies resulting in a download request from the MX4428).
For an autotest where remote device testing is enabled in the MX4428, and for all system
tests, all detectors which are capable of a remote alarm test are tested. The LEDs do not
operate and no alarms caused only by the remote test are returned to the MX4428. A device
with an external wiring fault or which is isolated, or in alarm or pre-alarm, is not subject the
test and is not reported. A device with a fault, other than external wiring, or which is in scan
fail scan fail, or relay checkback fail, or type mismatch, results in failure of the test (abnormal
at start). No filtering is applied during remote tests.