SECTION 8
SENSITIVITY ADJUSTMENT
8.1
On the fuse panel in the section above the fuses, a self-adhesive label shows 24 smoke detector sections
corresponding to the possible 24 modules located within the cabinet.
8.2
This table is used to record the sensitivities of the individual modules during each scheduled service. During each
service. new measurements are taken and recorded on a fresh label. These readings are then compared to the
previous readings to determine if dust is accumulating within the detector module's housings. The two readings
should be within 3 millivolts. The smaller the voltage reading. the closer the individual detector is to alarm.
8.3
The individual values of the various detectors may vary, but a typical maximum sensitivity as shipped would be a
reading of about 1.5 to 2.5VDC. The actual trip point of the detectors will be in the 7 to 10 millivolt range.
8.4
Decreasing value of delta V indicates that dust has collected in the receptacle or that paint is peeling. Dust
receptacle. If any white surface is showing, repaint with black vinyl matte emulsion.
8.5
If the presence of dust causes the reading to approach alarm (trip) conditions, those particular detectors may be
adjusted to a reduced sensitivity with a field adjustment potentiometer located on the circuit board within the
module. See Figure 8-3.
8.6
To measure the sensitivity of the individual detector module, two test receptacles appear on the front of each
detector module. The voltage reading should be taken by means of high impedence (minimum 5 megohms)
digital voltmeter, capable of reading on at least 3-1/2 digits.
8.7
Polarity is of no importance although test point 1 will normally be positive in relation to test point 2 during standby
conditions. The significant value is the voltage between the two points (delta voltage). This reading can be
expected to be 1000 millivolts or greater in any event and normally as indicated above.
8-1
