F4000 LCD Operator's Manual
Document No: LT0117
Operating Instructions - Point Functions
Page 8-14
19 April 2002
Issue 2.38
8.3.3 NOTES
(1)
The first time a sensitivity change is attempted, the FIP will determine if access is
permitted. This includes testing for the ability to write to the EEPROM (the hardware
link must be in the WRITE ENABLE position, or software EEPROM WRITE ENABLE
must be available), access to the EEPROM (processing is running, and there are no
Power Up, System or Automatic Tests running), and verifying the LCD Access
Password entered by the operator.
Changes to the sensitivities can only be made if the above conditions are met.
If the changes cannot be made due to the above conditions not being met, or due to
the AAR or MPR receiving its database or being used by other operators (e.g.
another operator is logged into the programming terminal, and is using the Analogue
Diagnostics to interrogate the AAR or MPR for point analogue values), then the LCD
will display
"Cannot Set Analogue Point Sensitivity"
.
(2)
The AAR software must support reception of the sensitivity data, otherwise a full
database transfer to the AAR will result.
(3)
All MPRs support reception of sensitivity data.
8.3.4 ANALOGUE LEVEL VERSUS SMOKE DENSITY
Analogue smoke detectors measure the amount of smoke in their chamber and convert it to
a number. This number is sent to the AAR or MPR, and processed to determine what
condition exists.
The analogue responder compares the current number returned by the detector with a
heavily filtered historical number, thereby cancelling the effects of contamination. The result
of the comparison is an indication of the actual amount of smoke detected. When the
difference exceeds the programmed sensitivity setting an alarm condition is annunciated.
The sensitivity setting for a detector can be adjusted to allow it to respond to smoke sooner,
or alternatively, to respond to smoke later, e.g. to reduce the effect of phenomena that
produce conditions similar to smoke.
To
increase
the detector sensitivity to smoke (i.e. generate alarm earlier), the sensitivity
setting is
decreased
.
To
decrease
the detector sensitivity to smoke (i.e. generate alarm at a higher level of
smoke), the sensitivity setting is
increased
.
The analogue thermal detectors return numbers that correspond to temperature. An alarm is
generated when the measured temperature exceeds the programmed sensitivity setting. In
addition, Type A detectors monitor the rate that the temperature is rising, and if it exceeds
the programmed limit for Rate of Rise, an alarm condition is annunciated.
