Temperature Sensing and Control:
Unlike the NTC thermistor with its ability to sense temperature accurately over a wide temperature range, the PTC thermistor is only useful as a temperature measuring device over a relatively short range of temperatures near the switch temperature. Because the resistance versus temperature characteristic of the PTC thermistor does not lend itself to an equation, most specifications are for the PTC thermistor to be a resistance value at some specific temperature plus or minus some tolerance. When the PTC is being used as a temperature sensor, the amount of current through the PTC must be small so as not to self-heat the thermistor and cause errors. Normally, it is not possible to use a PTC thermistor as a temperature sensor when it is in a self-heated mode of operation.
Thermistors Unlimited's solid-state over-temperature protectors are designed to sense the temperature of power transistors, heat sinks, chassis, etc. Construction consists of a small 0.1"-0.2" diameter positive temperature coefficient thermistor disc attached to an anodized aluminum mounting tab using thermally conductive epoxy.
The devices remain in their low resistance state at all temperatures below the switch temperature. When the switch temperature is reached or exceeded, they increase in resistance rapidly thereby limiting current to the drive circuitry to protect the critical components. Once the temperature decreases to a normal operating level, the device resets to its low resistance state.
To see our Data Sheets for our standard Over-Temperature Sensors click here.
| Part Number | Switch Temperature (°C) |
| SL20T-101-40 | 40 |
| SL20T-101-50 | 50 |
| SL20T-101-60 | 60 |
| SL20T-101-70 | 70 |
| SL20T-101-80 | 80 |
| SL20T-101-90 | 90 |
| SL20T-101-100 | 100 |
| SL20T-101-110 | 110 |
| SL20T-101-120 | 120 |
*Add -1 to Part Number for variations with 0.120" diameter ±0.005 mounting hole.
Specifications:
- Resistance @ 25°C: 100Ω ± 30%
- Maximum Voltage Rating: 50 V
- Maximum Operating Temperature: 150°C
- Switch Temperature: Temperature at which the resistance is two (2) times the resistance at 25°C
- Dielectric withstanding voltage: 50 VDC minimum between element and tab.
Note: Parts with resistance values or switch temperatures that are not listed are available. Contact us for more information.