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Types and Identification Methods of Varistors

by: Aug 16,2023 1081 Views 0 Comments Posted in PCB Basic Information


Varistors are commonly employed in circuits for overvoltage protection, such as shielding electronic components from damage caused by excessive voltage. When the voltage in the circuit exceeds a predetermined value, the varistor transitions into a conductive state, diverting the overvoltage to the ground, and thereby protecting other components. Different models of varistors exhibit distinct characteristics and find application in various scenarios. Thus, accurate identification of the varistor model is of utmost importance. This article provides a comprehensive exploration of varistor models and identification methods.

Varistor Model

The model of a varistor resistor typically consists of the following components:

  • Material: The material of the varistor resistor is usually zinc oxide (ZnO) or leaded glass (PbSiO3), etc.
  • Dimensions: The dimensions of the varistor resistor are typically described by two parameters: diameter and thickness.
  • Resistance Value: The resistance value of the varistor resistor is usually represented by a numerical figure, such as 10Ω, 100Ω, etc.
  • Rated Power: The rated power of the varistor resistor is typically indicated by a letter, for instance, A, B, C, etc.

Methods of Identifying Varistor Resistors

  • Visual Inspection: Varistors typically have a compact cylindrical appearance, covered with a layer of white or yellow insulation. Preliminary identification of the varistor type can be made by observing its appearance.
  • Check for Markings: Markings on varistors are usually printed on the insulation layer and include information such as the varistor model, resistance value, rated power, and more. Checking these markings allows for accurate identification of the varistor model.
  • Use of a Multimeter: Utilizing a multimeter enables the measurement of the varistor's resistance value and rated power, providing further confirmation of its model.
  • Reference Manufacturer Documentation: Varistor models and specifications are often available in the manufacturer's product manuals or on their websites. Confirming the varistor model and specifications can be achieved by referencing manufacturer documentation.


When identifying the model of varistors, the following points should be taken into consideration:

  • Choose appropriate tools and instruments, such as a multimeter, to ensure the accuracy and reliability of measurement results.
  • Pay attention to the rated power of the varistor to avoid exceeding its limits and causing damage.
  • Take the accuracy of the varistor into account and use suitable resistance meters or multimeters for measurement to minimize measurement errors.
  • Be mindful of environmental conditions affecting the varistor resistor, avoiding factors like temperature and humidity that could impact measurement results.

In summary, the model of a varistor typically comprises components such as material, dimensions, resistance value, and rated power. Identification can be carried out through methods including visual inspection, checking markings, using a multimeter, and referencing manufacturer documentation.

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