Thermistor vs. Varistor — What's the Difference?
By Maham Liaqat & Fiza Rafique — Updated on April 30, 2024
A thermistor is a temperature-sensitive resistor whose resistance changes with temperature, used primarily for temperature sensing and control; a varistor changes resistance in response to voltage surges, serving as a protector in electrical circuits.
Difference Between Thermistor and Varistor
Table of Contents
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Key Differences
A thermistor's resistance decreases as temperature increases if it is a Negative Temperature Coefficient (NTC) type, while a varistor, specifically designed for voltage protection, shows a decrease in resistance with an increase in voltage.
Thermistors are commonly used in applications like household appliances (e.g., ovens, refrigerators) for temperature measurement and control, whereas varistors are found in power supply units to protect against voltage spikes.
The operating principle of a thermistor is based on the temperature dependence of the electrical resistance of its semiconductor material, whereas a varistor operates based on the non-linear voltage dependence of its semiconductor material.
In terms of construction, thermistors are typically made of ceramic or polymer materials that exhibit significant changes in resistance with small temperature variations, while varistors are made of metal oxide materials, most commonly zinc oxide.
Accuracy and response time are critical for thermistors in temperature sensing applications, requiring precise calibration and often a stable environment, whereas the primary attribute for varistors is their ability to absorb and dissipate energy from transient voltage spikes rapidly.
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Comparison Chart
Function
Temperature sensing and control
Voltage surge protection
Sensitivity
Temperature
Voltage
Typical Material
Ceramic or polymer
Metal oxide (usually zinc oxide)
Application Example
Used in ovens and refrigerators
Used in power supply units
Key Characteristic
High sensitivity to temperature
High energy dissipation capability
Compare with Definitions
Thermistor
A resistor whose resistance varies significantly with temperature.
The thermistor in the circuit prevented overheating by adjusting the current flow.
Varistor
A voltage-dependent resistor with a non-linear voltage-current characteristic.
The varistor quickly clamped the unexpected voltage spike, saving the television.
Thermistor
Used in a wide range of consumer electronics and industrial applications.
Thermistors are crucial components in thermostats and automotive temperature controls.
Varistor
Protects circuits from high voltage surges.
A varistor was installed across the power line as a safeguard against lightning strikes.
Thermistor
Available mainly in NTC and PTC types, referring to negative and positive temperature coefficients, respectively.
The NTC thermistor was chosen for its rapid response to temperature drops.
Varistor
Made primarily from metal oxide materials.
The metal oxide varistor offered robust performance in harsh environments.
Thermistor
Often embedded within thermal protective circuits.
The thermistor protected the motor from thermal overload.
Varistor
Characterized by its ability to absorb transient voltages.
The varistor absorbed the surge caused by the industrial equipment startup.
Thermistor
Commonly used as a temperature sensor in electronic devices.
Engineers installed a thermistor in the device for precise temperature monitoring.
Varistor
Used in both household and industrial electronic installations.
Varistors are integral in safeguarding both residential and industrial electrical systems.
Thermistor
A thermistor is a type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors. The word is a combination of thermal and resistor.
Varistor
A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode.
Thermistor
A resistor made of semiconductors having resistance that varies rapidly and predictably with temperature.
Varistor
(electronics) An electronic component having a variable resistance; used to protect circuits against power surges.
Thermistor
(electronics) A resistor whose resistance varies rapidly and predictably with temperature and as a result can be used to measure temperature.
Thermistor
A semiconductor device made of materials whose resistance varies as a function of temperature; can be used to compensate for temperature variation in other components of a circuit
Common Curiosities
What is a thermistor used for?
It's used for measuring and controlling temperature in various devices.
How does a thermistor work?
It changes resistance with changes in temperature.
Can a thermistor be used for high temperature applications?
Yes, especially ceramic thermistors, but the specific range depends on its design.
How accurate are thermistors?
They are highly accurate, particularly in controlled environments.
What are the types of thermistors?
There are NTC (Negative Temperature Coefficient) and PTC (Positive Temperature Coefficient) thermistors.
Can varistors prevent all types of electrical surges?
They are very effective against transient surges but not for sustained high voltage.
How does a varistor work?
Its resistance decreases rapidly with an increase in voltage across it.
What is the main material of a varistor?
Metal oxides, typically zinc oxide.
What is a varistor used for?
It is used to protect circuits from high voltage surges.
How do I choose a varistor for my circuit?
Selection depends on the maximum varistor in circuit.
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Written by
Maham Liaqat
Co-written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
