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Positive temperature coefficient of resistivity anomaly at the critical temperature in these devices has opened up numerous avenues of practical applications in the area of temperature control and heat protection. Because of their very high temperature coefficient of resistivity (> 25 ohms / o C) PTC thermistors are quite superior and more efficient than NTC thermisistors for above applications.
APPLICATIONS : As a temperature controller there are two typical applications of PTC thermistors. One is for a self heating and the other is for a heat sensing element. The typical examples of use as a self heating element are, heater, thermostat etc. and popular examples where PTC thermistors are exclusively used as heat sensing elements are a.c. induction motor over heat protectors, water cooled engine overheat warning degaussing coil of Colour TV etc.
PTC thermistors can also be used for monitoring changes in environment such as liquid level sensing, air flow indication and as current limiters.
The small miniature size of these devices allows a quick response to environmental temperature changes and its solid state nature gives distinct service advantages over alternative devices.PTC thermistors have been designed primarily for temperature sensing applications. They confirm to IEC specifications and are particularly suited to overheat protection of electric motors, transformers, compressors and many other types of industrial equipments.
These thermistors cannot normally be used directly in series with the relay, hence it is recommended to employ an associated sensing or trigger circuit to operate a relay or thyristor circuit.Because each thermistors is designed to be 1000 ohms (nominal resistance value) at the reference the temperature, the same design of sensing circuit can be used for each type.
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The small miniature size of these devices allows a quick response to environmental temperature changes and its solid state nature gives distinct service advantages over alternative devices.PTC thermistors have been designed primarily for temperature sensing applications. They confirm to IEC specifications and are particularly suited to overheat protection of electric motors, transformers, compressors and many other types of industrial equipments.
These thermistors cannot normally be used directly in series with the relay, hence it is recommended to employ an associated sensing or trigger circuit to operate a relay or thyristor circuit.Because each thermistors is designed to be 1000 ohms (nominal resistance value) at the reference the temperature, the same design of sensing circuit can be used for each type.
OUTLINE :
The dimensions of PTC thermistors after insulation are as follows. :
TYPICAL DIMENSIONS OF PTC THERMISTORS |
RATINGS OF PTC THERMISTORS
Tr. (oC) |
Lead Color Code |
Tr. (oC) |
Lead Color Code |
Tr. (oC) |
Lead Color Code |
60 |
Yellow |
110 |
Brown - Brown |
150 |
Black - Black |
80 |
White - White |
120 |
Grey - Grey |
160 |
Blue - Red |
90 |
Green - Green |
130 |
Blue - Blue |
170 |
White - Green |
100 |
Red - Red |
140 |
Blue - Black |
180 |
Yellow Red |
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LEADS :
Standard leads are 7 / 0.2 mm (or max. cross section are 0.3 mm2 ) silvered copper flexible cable with PTFE (Teflon) insulation. |
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