Self-heating effect and heat capacity of thermistor

Although most NTC thermistors are typically suitable for use in the temperature range of -55 ° C to 200 ° C and provide accurate readings, the special series of NTC thermistors can be close to zero (-273.15 ° C) and Those designed for use above 150 °C. The temperature sensitivity of the NTC sensor is expressed as "percent C change per degree". Typical values for temperature sensitivity range from -3° to 6°C, depending on the materials used and the specifics of the production process.

1.Self-heating effect

The self-heating effect is a phenomenon that occurs when current passes through the NTC thermistor. Since the thermistor is basically a resistor, it dissipates power in the form of heat when current flows. Heat is generated in the thermistor core, affecting measurement accuracy. The extent to which this happens depends on the magnitude of the current, the environment (whether liquid or gas, whether the NTC sensor has any flow, etc.), the temperature coefficient of the thermistor, the total area of the thermistor, and so on. The resistance of the NTC sensor and the fact that the current through it depends on the environment is often used in liquids such as storage tanks.

2. Heat capacity

The heat capacity represents the amount of heat required to raise the temperature of the thermistor by 1 ° C, usually expressed in mJ / ° C. When using an NTC thermistor sensor as a surge current control device, it is important to know the exact heat capacity because it defines the response speed of the NTC temperature sensor.