Temperature-sensing cable type temperature measurement. The sensing cable is shorted and the alarm signal is sent to the control system when the cable temperature exceeds the fixed temperature value.
The disadvantage of common type temperature sensing cable is: destructive alarm, alarm temperature fixed, fault signal is not complete, system installation and maintenance work is not convenient, the equipment is easy to damage; analog linear temperature-sensitive cable can only be a certain part of the line as alarm unit, so it can not accurately locate a point generated by the alarm signal. Thermistor type temperature measurement.
The use of thermistor can be measured cable temperature values, but are analog output, the need for a signal amplification and a/D conversion to be received, each thermistor needs an independent wiring, wiring complex and thermistor easy to damage, maintenance of large, the sensor does not have self-test function, the need for regular calibration. Infrared sensor type temperature measurement. Infrared sensing is the use of all the temperature above the absolute 0 degrees in the surrounding space is constantly emitting infrared radiation energy, the object's infrared radiation energy size and its distribution by wavelength and its surface temperature has a very close relationship. Therefore, by measuring the infrared energy of the body's own radiation, the surface temperature can be measured accurately.
Infrared sensor is non-contact measurement, so it has very good safety, its disadvantage is that it is affected by the emissivity of the object, the environment and the air mist, and the anti-interference ability is poor in the temperature measurement. Thermocouple type temperature measurement. The thermocouple transmission signal needs the special compensation line, and the transmission distance should not be too long, does not adapt the cable head distribution surface to be very widespread actual situation; thermistor is usually platinum resistance, the general need to use three-wire transmission, balanced bridge type output, transmission distance is not too long, and anti-interference ability is poor.