Essential Electrical Skill: How to Verify the Functionality of an Analog Multimeter

An analog multimeter (AMM) is an essential tool for electrical testing and troubleshooting. It measures voltage, current, and resistance, and its accuracy is crucial for reliable results. Checking the functionality of an AMM before use is vital to ensure accurate readings. Here’s a comprehensive guide on how to check if an analog multimeter is working:

1. Visual Inspection

Begin by visually inspecting the multimeter for any physical damage, such as cracks or dents. Check the leads for any cuts or breaks in the insulation. If any visible damage is present, do not use the multimeter.

2. Battery Check

Most AMMs are powered by 9-volt batteries. A weak or dead battery can affect the accuracy of the readings. To check the battery:

• Turn the selector switch to the “DCV” range.
• Connect the positive test lead to the positive terminal of the battery and the negative test lead to the negative terminal.
• The meter should read around 9 volts. If the reading is significantly lower, replace the battery.

3. Zero Adjustment

Before taking any measurements, it’s important to zero the multimeter. This ensures that the pointer is resting exactly on the zero mark when there is no voltage or current flowing through it.

• Set the selector switch to the lowest “DCV” range.
• Touch the test leads together.
• Use the zero adjustment screw (usually located near the display) to adjust the pointer until it rests on the zero mark.

4. Voltage Measurement

To check the voltage measurement function:

• Set the selector switch to the appropriate “DCV” range based on the expected voltage.
• Connect the positive test lead to the positive terminal of the voltage source and the negative test lead to the negative terminal.
• The meter should display the voltage reading.
• Compare the reading with a known voltage source or a second multimeter for accuracy.

5. Current Measurement

To check the current measurement function:

• Set the selector switch to the appropriate “DCA” range based on the expected current.
• Break the circuit where you want to measure the current.
• Connect the multimeter in series with the circuit, with the positive test lead connected to the positive side of the circuit and the negative test lead connected to the negative side.
• The meter should display the current reading.
• Compare the reading with a known current source or a second multimeter for accuracy.

6. Resistance Measurement

To check the resistance measurement function:

• Set the selector switch to the appropriate “Ω” range based on the expected resistance.
• Connect the test leads to the resistor or component you want to measure.
• The meter should display the resistance reading.
• Compare the reading with a known resistor or a second multimeter for accuracy.

7. Calibration

If the AMM consistently provides inaccurate readings, it may need to be calibrated. Calibration involves adjusting the internal components of the multimeter to ensure that it meets specified accuracy standards. It’s recommended to have the multimeter calibrated by a qualified technician using specialized equipment.

Troubleshooting Common Issues

• Erratic Pointer Movement: Clean the terminals and test leads, and check for loose connections.
• No Reading: Check the battery, zero adjustment, and test leads.
• Inaccurate Readings: Calibrate the multimeter or compare readings with a known source.
• Overload: If the measured value exceeds the multimeter’s range, the meter may indicate an overload. Set the selector switch to a higher range.

FAQ

Q: Why is it important to check the battery of an analog multimeter?
A: A weak battery can affect the accuracy of the readings.

Q: How often should I calibrate an analog multimeter?
A: The frequency of calibration depends on the usage and accuracy requirements. Generally, it’s recommended to calibrate every 6-12 months.

Q: What are some signs of a faulty analog multimeter?
A: Erratic pointer movement, no readings, inaccurate readings, and overload indications.