The Series 65A Heat Detector works by monitoring heat using a dual thermistor network which provides a voltage output proportional to the external air temperature.
Series 65A 135F Heat DetectorDownload PDF
The Heat Detector has a common profile with the Series 65A ionization and photoelectric detectors but has a low air flow resistance case made of white self-extinguishing polycarbonate.
A pair of matched negative temperature co-efficient (NTC) thermistors are mounted on the internal PCB in such a way that one thermistor is exposed to give good heat contact with the surrounding air while the other thermistor is heat insulated.
Under normal conditions both thermistors are in heat equilibrium and have the same value of resistance. If air temperature increases rapidly the resistance of the exposed thermistor becomes less than that of the insulated thermistor. The ratio of the resistance of the thermistors is monitored electronically and an alarm is initiated if the ratio exceeds the factory pre-set level. This determines the ‘rate- of-rise’ response of the detector.
- Ideal in environments that are dirty or smoky under
- Wide operating voltage
- Flashing LED option
- Flashing LED and magnetic test switch option