Safety usage guide for digital multimeters: Precautions and prevention of common errors

Safety Operating Guide

◆ Preparations before measurement

Before using the multimeter, make sure that the selector switch is set correctly. Developing this habit will significantly reduce the risk of damaging the meter. When choosing the range, try to make the pointer point to about two-thirds of the full scale to ensure the accuracy of the reading. If you are unsure about the magnitude of the voltage or current being measured, it is recommended to first select a larger range and then adjust the range based on the actual reading. When measuring resistance, always reset the meter after changing the range to ensure the accuracy of the reading. If you cannot reset to zero, it may be due to insufficient battery voltage in the meter. In this case, replace the battery. When measuring resistance in an online context, make sure to cut off the power supply first. Also, confirm if there are any other components connected in parallel with the measured resistor. If necessary, open one end of the resistor from the circuit for measurement. For circuits containing electrolytic capacitors, discharge them before measurement. When using the multimeter, avoid touching the metal part of the meter leads to prevent electric shock accidents. Additionally, touching the metal part of the meter leads can affect the reading.

◆ Precautions during measurement

When measuring DC voltage, connect the red probe to the positive terminal and the black probe to the negative terminal to prevent damage to the multimeter due to incorrect polarity. If the polarity is uncertain, you can first select a larger range and quickly touch the measured point with the meter probes to determine the correct polarity by observing the pointer's swing direction. It is particularly important not to mistakenly use the mA or ohm range to measure voltage. When measuring current, never cross-connect the two probes to the power supply as it can damage the meter head. Also, be aware that most multimeters can only measure DC current and cannot measure AC current.

◆ Safety measures after measurement

After use, place the range switch in the highest voltage position. For multimeters with short-circuit or open circuit functions, position them accordingly to prevent others from mistakenly using and damaging the instrument.

◆ Common errors and prevention

1. Replace the original fuse of the multimeter with a cheap fuse. Please note that if your digital multimeter complies with the electrical safety standards indicated on it, then use a fuse with special safety features to ensure it can quickly open before severe overload, thereby protecting the instrument and personal safety. When replacing the fuse of a digital multimeter, be sure to select a fuse that complies with safety specifications and is allowed for use.

2. Replace the fuse of the multimeter with a metal wire or metal sheet. Although this may seem like a quick solution, in cases where no suitable fuse is found, such an alternative may pose serious safety hazards.

3. Use tools that are not suitable for the current task. Choosing a digital multimeter that is suitable for a specific task is crucial. First, ensure that the digital multimeter has the correct CAT (electrical safety) rating to adapt to different testing scenarios; second, ensure that its maximum continuous working voltage meets the actual testing requirements. When measuring live circuits, try to do it with power off. If you really need to measure live circuits, use the correct insulated tools and take necessary protective measures, such as wearing ear protection, safety glasses, arc protection mask, and insulated gloves. Also, ensure you are standing on an insulating pad and wearing flame-resistant work clothes to avoid the risk of metal items like jewelry causing danger.

5. Ignore the importance of the test leads. The test leads are also a key factor in ensuring the safety of the digital multimeter. Select test leads with the appropriate CAT electrical safety rating for the corresponding work and ensure they have safety features such as double insulation, protective input connectors, finger guards, and anti-slip surfaces.

6. Avoid performing tests with both hands. When measuring live circuits, it is recommended to put one hand in your pocket to reduce the risk of forming a closed circuit through the chest and heart. Try to hang or place the multimeter, avoid holding it, and minimize exposure to transient voltages as much as possible. At the same time, in measurements with higher risks, additional preventive measures should be taken to reduce hazards and the risk of arc flash, such as using protective equipment as stipulated in national electrical regulations to provide arc protection.