How to test the quality of the switch with a multimeter

How to test the quality of the switch with a multimeter

In electronic maintenance and circuit testing, the quality of the switch directly affects the normal operation of the equipment. Using a multimeter to test a switch is a simple and effective way. This article will introduce in detail how to use a multimeter to measure the quality of the switch, and attach structured data to help readers quickly master the operation steps.

1. Basic principles of measuring switches with a multimeter

The core function of the switch is to control the on and off of the circuit. Under normal circumstances, the resistance is close to 0Ω when the switch is closed, and the resistance is infinite (or extremely high) when it is open. A multimeter can determine whether the switch status is normal by measuring the resistance value.

2. Measurement steps

Here are the specific steps for using a multimeter to measure the quality of a switch:

1. Preparation

(1) Ensure that the switch is completely disconnected from the circuit to prevent other components from interfering with the measurement results.
(2) Adjust the multimeter to the resistance measurement range (usually the Ω range) and select the appropriate range (such as 200Ω or 2kΩ).
(3) Short-circuit the multimeter probe to confirm that the zero point calibration is normal (displays 0Ω or close to 0Ω).

2. Measure the closed state

(1) Turn the switch to the "closed" position.
(2) Use the multimeter probe to touch the two contacts of the switch.
(3) Observe the reading: Normally it should be 0Ω or a minimum value (such as below 0.5Ω). If the resistance is too high, it means the switch has poor contact.

3. Measure the disconnected state

(1) Turn the switch to the "off" position.
(2) Repeat the test pen contact operation.
(3) Normally it should display "OL" (over range) or "1" (infinity). If there is a resistance value, it means the switch is leaking or the insulation fails.

3. Common problems and solutions

1. The measurement results are unstable

Possible reasons: The switch contacts are oxidized or dirty.
Solution: Clean the contacts with alcohol, or lightly polish the contact surface.

2. The closed state resistance is too large

Possible reasons: Spring aging or mechanical structure deformation.
Solution: Adjust spring tension or replace switch.

4. Advanced skills

1. Measurement with indicator switch

This type of switch has a parallel indicator light circuit inside. It is necessary to disassemble the circuit and measure the switch part separately. Otherwise, misjudgment will occur due to the shunting of the indicator light.

2. Multi-position switch detection

For multi-position switches (such as rotary switches), it is necessary to test the on-off status of each gear position and record the corresponding contact relationship.

5. Safety precautions

1. Be sure to turn off the power before measurement to avoid the risk of short circuit.
2. Do not operate in humid environment to prevent electric shock.
3. For high-voltage circuit switches, it is recommended to use special high-voltage detection equipment.

Through the above methods, you can quickly and accurately determine the working status of the switch. Regular inspection of switches can effectively prevent circuit failures and ensure safe operation of equipment.