How do you test for varistor? Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown.
What is a varistor used for?
Varistors are used to protect a circuit from high voltage surges. When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit. A capacitor may be installed across the signal lines. However, this capacitor cannot suppress voltage surges.
What is the symbol for a varistor?
Varistor symbol The varistor circuit symbol can be seen to be very similar to that of a thermistor. It consists of the basic resistor symbol of a rectangle with a diagonal line through it that has a small added section parallel to the body of the resistor symbol. This indicates the no-linear nature of the varistor.
How do I choose a varistor?
Choose a varistor with an energy absorption rating that equals or slightly exceeds the energy values associated with the event the circuit may experience. If, however, the transient voltage is due to an external event, the magnitude of the source energy is unknown.
Can a varistor go bad?
The varistor, normally having a very high resistance, responds to the voltage spike by absorbing its energy with a very low resistance. The varistor will likely be wired to a fuse holder. If the varistor is visibly burnt through or broken, it is bad; replace it.
What is the difference between fuse and varistor?
Unlike the fuse or circuit breaker which offers over-current protection, the varistor provides over-voltage protection by means of voltage-clamping in a similar way to the zener diode. In many ways the varistor looks similar in size and design to a capacitor and is often confused as being one.
How many types of varistor are there?
There are two main types of Varistors available in market namely the silicon carbide and metal oxide Varistors.
What is the working principle of varistor?
A varistor does not obey Ohm’s law and hence it is not like an ohmic resistor. It is basically a non-ohmic resistor that does not follow Ohm’s law and hence it is also called a non-linear resistor or a voltage-dependent resistor.
Is a varistor a diode?
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.
What is a varistor and how does it work?
A varistor is a device with a non-linear volt-ampere characteristic. When the voltage applied to the varistor is lower than its threshold value, the current flowing through it is extremely small, which is equivalent to a resistor with infinite resistance, vice versa. The most common varistor is a metal oxide varistor (MOV).
How do you test a varistor with a multimeter?
How to Test a Varistor. Turn the multimeter on and set it to read resistance times 1000 ohms. Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown.
What is the current-voltage curve of a varistor?
Therefore, the current-voltage characteristic curve of a varistor is highly non-linear: high resistance at low voltage and low resistance at high voltage. Metal oxide varistors are currently the most common voltage clamping devices and can be used for various voltages and currents.
What is the mcov of a varistor?
MCOV refers to the maximum DC voltage (UDC )or the maximum AC voltage effective value (URMS) that the varistor can withstand for a long time. Varistors have a very special characteristic: long-term static power is very small, and instantaneous dynamic power is very large.
