Can a thermistor measure very high or very low temperatures?

In one line

The rule

A thermistor is a type of resistor whose resistance changes a lot with temperature, but only within a certain temperature range.

There is no single formula for all thermistors, but the general relationship is: R = R₀ × exp[B × (1/T - 1/T₀)] where R = resistance at temperature T (in kelvin), R₀ = resistance at reference temperature T₀, B = a constant for the material.

Let's understand it simply

Imagine a thermistor like a cricket bat made of chocolate. It works well when the weather is cool, but if it gets too hot, the bat melts. If it gets too cold, the bat becomes hard and brittle. Similarly, a thermistor works well only in a certain temperature range. If you try to use it in a very hot or very cold place, it stops working properly or even breaks.

How it works

1. A thermistor is made from special materials (like metal oxides) that change resistance with temperature.
2. When temperature increases, the resistance of an NTC (Negative Temperature Coefficient) thermistor decreases.
3. When temperature decreases, the resistance increases.
4. But if the temperature goes too high, the material can melt or break down.
5. If the temperature goes too low, the material can stop responding or crack.

The story behind it

Thermistors were invented in the 1930s by Samuel Ruben. He was looking for a simple way to measure temperature using electricity. The word "thermistor" comes from "thermal resistor." These devices became popular because they are cheap and easy to use in circuits.

Where you see it in real life

• Electric kettles: To sense when water is hot enough → thermistor works in the safe range (about 0°C to 100°C).
• Refrigerators: To check if the inside is cold → works at low, but not extremely low, temperatures.
• Battery packs: To stop charging if battery gets too hot → thermistor works in a moderate range.
• Air conditioners: To measure room temperature → not used for very high or low extremes.
• Medical thermometers: For body temperature (about 35°C to 42°C) → safe and accurate in this range.

Why it matters

• Thermistors are cheap and quick for measuring normal temperatures in daily appliances.
• They help protect devices from overheating or freezing.
• They are used in many gadgets, but only where the temperature stays within a safe range.
• For extreme temperatures (like a furnace or liquid nitrogen), other sensors (like thermocouples or RTDs) are used.

Common mistakes

• Thinking a thermistor can measure any temperature: It has a limited range, usually between −50°C and 150°C.
• Using the wrong type of thermistor: Some are made for higher or lower ranges, but none cover all extremes.
• Forgetting that too much heat or cold can damage the thermistor permanently.

Remember it

Thermistors are like milk—they spoil if it gets too hot or too cold. Use them only in their safe temperature range.