How do you test a circuit board 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.
How do you test electronic components on a circuit board?
Testing the resistors on a printed circuit board can be done by firstly isolating the resistors so that the results won’t be skewed by other components on the circuit board. You can then use a digital multimeter or an analogue meter to measure the results.
How do you test a circuit board for faults?
How to Find a Fault in a Circuit Board
- Make sure it’s plugged in tight and the pins are clean.
- Check to see if all the circuit boards (CB) are plugged in tightly.
- Check individual plug-in components.
- Look for water or foreign objects anywhere on the circuit board.
- Check secondary wiring plugs.
How do you tell positive and negative on a circuit board?
Sometimes it’s easiest to just use a multimeter to test for polarity. Turn the multimeter to the diode setting (usually indicated by a diode symbol), and touch each probe to one of the LED terminals. If the LED lights up, the positive probe is touching the anode, and the negative probe is touching the cathode.
How to test a varistor with a multimeter?
Another way to test a varistor for breakdown with a multimeter is to measure resistance. It is necessary to set the device to the maximum measurement limit, in most devices it is 2 MΩ (megaohms, designated as 2M or 2000K). Resistance should be equal to infinity.
What is a varistor?
Varistors are components which protect electronic circuitry from excess power such as that offered in the case of transient voltages. Transient voltages are high-magnitude spikes of voltage which can occur in a circuit. They can be caused by a number of factors, such as lightning.
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.
How does voltage affect the resistance of a varistor?
The more the AC line voltage increases, as it does in a serious power surge, the more the varistor’s resistance drops. So more and more current will flow through the varistor during a great power surge, since it offers such small resistance when voltage is great.