A temperature coefficient of a resistor is a means of indicating the value of a resistor varies when the temperature changes. A resistor is an electronic thing that has a resistance and controls electricity that flows through a circuit. A resistor’s resistance does not constantly stay the same as stated. Instead, the resistor can change its value, either going up or down depending on the temperature.
The temperature coefficient of a resistor is measured in parts per million per degree Celsius (or simply ppm per degree C). For example, if a resistor has a temperature coefficient of +100 ppm per degree Celsius, this indicates that there will be a resistance value increase of 0.01% or one hundred ppm, for every 1° C increase in temperature. Therefore, if the temperature changes by one degree C the resistance will become less (go down, or switch states) based on the ppm. It is also possible to have a negative temperature coefficient in which case the resistance goes down as the temperature increases.
Broadly speaking, two types of resistors, positive temperature coefficient (PTC) and negative temperature coefficient (NTC). A PTC resistor has a resistance that increases as the temperature rises and an NTC resistor has a resistance that decreases with an increase in temperature. You will find that some applications use PTC resistors and some applications use NTC resistors. For example, NTC resistors can be used to create temperature sensors and NTC resistors can help protect electronic devices from overheating.
It is necessary to understand the temperature coefficient when designing electronic devices that will be expected to operate correctly over diverse temperature ranges. For example, within electronic devices such as smartphones, satellites, and other thermally dynamic environments, the temperature can swing and vary extremely. If a resistor becomes unstable in resistance tolerance, the whole circuit must will cease operation and/or provide outrageously erroneous readings. For that reason, it is reasonable engineering practice to utilize resistors with a low temperature coefficient of resistance specification for applications where the tolerance and accuracy are critical.
In summary, the temperature coefficient demonstrates the variable resistance of a resistor to temperature. The temperature coefficient can also be used by an engineer to differentiate resistor types and specifications in various environments and electrical or electronic device. Depending on material and physical structure when referring to temperature coefficients, it is important to understand if the resistance is increasing or decreasing with temperature.
