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 /  PTC Thermistor  /  NTC Thermistor

PTC Thermistors Limit Temperature Sensor

Radial Leaded Epoxy Resin Coated PTC thermistor Limit Temperature Sensor Engineering Drawing Metal tag lug PTC Thermistors Limit Temperature Sensor Engineering Drawing
PTC Thermistors Limit Temperature Sensor Description

PTC (positive temperature coefficient)thermistor switches at one particular temperature. Making use of the characteristics that the resistance of PTC thermistor increases sharply above curie temperature, when ambient temperature increases abnormally, protective circuit installed PTC thermistor will turn on or cut off loop through resistance changing, achieving thermal protection purpose. PTC thermistor protect such equipment and components as motors, transformers, power transistors and thyristors against over-temperature. A PTC thermistor is less expensive than a thermostat, and its switch temperature can be more accurately specified. It is also smaller and easier to design-in to electronic circuitry. Therefore PTC thermistor can be ideal devices for temperature detection, monitoring, indicating, limiting and over (excessive) temperature protection.

Typical Application of PTC Thermistor for Temperature Protection and temperature limiting sensors
¡¤Limit temperature measurement of Industrial electronics application.
¡¤Power supplies, switch power supply.
¡¤Home appliances, such as dish washers, washing machines, ironing machines, electric cookers, etc.
¡¤Electronic data processing and communications engineering (DC/DC converters).
¡¤Motor windings overheating Protection.
¡¤Automotive electronics.
¡¤Semiconductor heatsinks, enclosure panels, temperature-limited transistors.
¡¤Lighting applications.
PTC Thermistors Limit Temperature Sensor for Industrial Application

A PTC thermistor can be used effectively to detect whether a temperature limit in industrial equipment, liquids, etc, is exceeded. The PTC thermistor is mounted in thermal contact with the medium that has to be protected from overheating. When the rated temperature limit of the medium is reached, the resistance of PTC thermistor increases abruptly.In connection with a control unit, this signal can be used to automatically switch the power supply of a load.

Features of PTC Thermistor for Temperature Protection and temperature limiting sensors

¡¤2 Outlook construction: A-radial leaded epoxy resin coated form, B-metal tag lug form. Screw type metal cases or other construction can be made upon customer request.
¡¤PTC Thermistor Protection temperature 60C to 130C. 60C, 70C, 80C, 90C, 100C, 110C, 120C, 130C.
¡¤Quick response.
¡¤Long stability.
¡¤Small dimension, convenient for installation.
¡¤Do not need to be reset after protection.

Temperature Sensing Protection PTC Thermistor Operating Principle

As in fig. 1, in normal ambient temperature, PTC thermistor resistance Rp lower than Rs, lower output voltage. When ambient temperature exceeds set temperature, PTC thermistor resistance Rp increases rapidly, and exceeds Rs, and leads Vo increases to high enough voltage, and cause tripping.

PTC thermistors for temperature protection operating principle

Fig.1

PTC thermistor for temperature protection operating principle
Examples of circuit temperature sensing and protection by PTC thermistor
PTC Thermistors for temperature compensation and overheat sensing of transistors

Fig 3 (1) shows a basic circuit for temperature compensation. In biasing the transistor, the resistance of PTC thermistor is used. If the transistor overheats, the PTC thermistor will heat up as well. As the PTC thermistor passes the switch temperature, it will go high resistance and unbiased the circuit, and turning off the transistor. In case of Fig. 3(2) and 3(3), it also can be used as an over heat sensor as well.
When PTC thermistor is used for temperature compensation, it does not change the input impedance, like a negative temperature coefficient Thermistor (NTC Thermistor), because the PTC thermistor is not connected to input circuit in parallel. Therefore, the PTC thermistor is suitable for circuits which do not need a change of input impedance as a pulse circuits, regional amplifier, and measurement equipment.
PTC Thermistor for Transistor temperature compensation and protection circuit

Fig.3 PTC Thermistor for Transistor temperature compensation and protection circuit
More than two pieces of PTC thermistor can cover multi hot spots working with a comparator. Fig. 4 shows basic circuit idea to connect multiple PTC thermistors in series. When One PTC thermistor detects overheat at least, a comparator can work by the sharp temperatureresistance characteristic. It easily allows changing a number of PTC thermistor or sensing temperature in the same basic circuit design.
Multiple PTC Thermistors for temperature protection circuit
Fig.4 Multiple PTC Thermistors for temperature protection
PTC Thermistor for motors and transformers Overheat sensing
A PTC Thermistor can be used for the overheat sensing of motors, transformer winding, bearings, power transistors, and other machinery. Fig. 5(1) shows an example of overheat sensing for motor using a relay. In case of small regular operating current, the circuit can be directly stopped by PTC Thermistor. In case of larger regular operating currents, the circuit can be stopped by using the PTC Thermistor with a relay or a thyristor. In either case, PTC Thermistor is a very easy to use device, because it¡¯s small, light, and a two terminals device.
PTC Thermistors for motor transformer temperature protection circuit
Fig.5 PTC Thermistors for motor transformer temperature protection
PTC Thermistor for For temperature indication
Fig. 6 shows most simple example of a temperature indicator. Temperature is sensed by PTC Thermistor. If the target temperature is exceeded, a neon tube lights up.
PTC Thermistors for temperature indication circuit
Fig.6 PTC Thermistors for temperature indication
PTC thermistor for Overheat sensing circuit
Fig. 7 PTC thermistor for Overheat sensing circuit
PTC thermistors for overheat protection circuit
Fig. 8 PTC thermistors for overheat protection circuit
AMWEI PTC Thermistors Limit Temperature Sensor for Over-temperature Protection Data Sheet
Part number Protection
temperature
TS
£¨Centigrade£©
Resistance @25C
R25
£¨Ohm£©
Resistance
@ TS -15C
RS-15
£¨Ohm£©
Resistance
@ protection
temperature
RS
£¨Ohm£©
Max. current
Imax
£¨mA£©
Max. voltage
Vmax
£¨V£©
AMZ6-101RT60 60C 100 Ohm max 330 Ohm max 470 Ohm min 100mA 30V
AMZ6-101RT70 70C 100 ohm max 330 ohm max 470 ohm min 100mA 30V
AMZ6-101RT80 80C 100 ohm max 330 ohm max 470 ohm min 100mA 30V
AMZ6-101RT90 90C 100 ohm max 330 ohm max 470 ohm min 100mA 30V
AMZ6-101RT100 100C 100 ohm max 330 ohm max 470 ohm min 100mA 30V
AMZ6-101RT110 110C 100 ohm max 330 ohm max 470 ohm min 100mA 30V
AMZ6-101RT120 120C 100 ohm max 330 ohm max 470 ohm min 100mA 30V
AMZ6-101RT130 130C 100 ohm max 330 ohm max 470 ohm min 100mA 30V
AMZ6-331RT60 60C 330 ohm max 1.5k ohm max 2.2k ohm min 100mA 30V
AMZ6-331RT70 70C 330 ohm max 1.5k ohm max 2.2k ohm min 100mA 30V
AMZ6-331RT80 80C 330 ohm max 1.5k ohm max 2.2k ohm min 100mA 30V
AMZ6-331RT90 90C 330 ohm max 1.5k ohm max 2.2k ohm min 100mA 30V
AMZ6-331RT100 100C 330 ohm max 1.5k ohm max 2.2k ohm min 100mA 30V
AMZ6-331RT110 110C 330 ohm max 1.5k ohm max 2.2k ohm min 100mA 30V
AMZ6-331RT120 120C 330 ohm max 1.5k ohm max 2.2k ohm min 100mA 30V
AMZ6-331RT130 130C 330 ohm max 1.5k ohm max 2.2k ohm min 100mA 30V

AMWEI PTC thermistors limit temperature sensor code


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