Remember the most taboo measurement method for DMMs! ! It is strictly forbidden to measure any electronic ignition (voltage of high-voltage lines of automobiles and motorcycles, gas stoves, gas water heaters, etc.) and high-voltage generators (voltage of electronic mosquito swatters and electric rods, etc.)! ! Once the measurement is performed, no personal safety accident will occur, but the meter will be scrapped due to the ignition and breakdown of the integrated block inside the advanced multimeter! ! … don't forget! ! …
Pointer multimeter use precautions
It is a good habit to develop a good habit of using a multimeter, that is, to check whether the position of the stop is correct before each measurement. With such a habit, the chance of burning the watch will be greatly reduced.
The range should be selected so that the pointer indicates near two-thirds of the full scale, and the reading is more accurate. If you do not know the magnitude of the measured voltage and current, you should select a large range block, and then re-adjust the range according to the size of the reading to make the reading accurate.
When measuring resistance, it is necessary to re-zero after changing the range block, so that the reading can be accurate. If it cannot be adjusted to zero, it means that the battery voltage in the meter is insufficient, and the battery should be replaced.
When measuring resistance online, the power supply should be cut off to operate, and attention should be paid to whether there are other components forming a parallel circuit with the resistance to be measured. If necessary, one end of the resistance can be welded from the circuit and then measured. For circuits with electrolytic capacitors, discharge the capacitors before measuring.
When using the multimeter, it is necessary to develop the habit of not touching the metal part of the test lead to prevent electric shock accidents. At the same time, when measuring resistance, if you touch the metal part of the test lead, the reading will be affected.
When measuring DC voltage, connect the red pen to "+" and the black pen to "-" to prevent the reversed polarity from causing the needle to be deflected and damage the needle. If you do not know the positive and negative polarity, you can first dial to the high-range gear, quickly touch the measured point with the test pen, and observe the swing direction of the pointer to determine the correct polarity. In particular, do not use the mA block or electrical block to measure the voltage by mistake, otherwise the meter will be burned out.
When measuring the current, never connect the two test leads across the power supply, so as not to burn the meter head. A general multimeter can only measure DC current, not AC current.
After the meter is used up, the range switch should be placed in the highest voltage gear. For multimeters with short-circuited or disconnected gears, they should be placed in the corresponding gears to prevent others from being careless and damaging the meter.
So in daily work, many people will have some wrong methods when using multimeters. Let's take a look at it for everyone. Have you ever done the same?
1. Replace the fuse of the original multimeter with a cheap fuse. If your digital multimeter (DMM) meets the electrical safety standards it identifies, then the fuse should be a fuse with a special safety feature that guarantees quick disconnection before severe overload occurs for instrument and personal safety. When you need to replace a DMM's fuse, be sure to use a fuse that meets safety regulations and is approved for use.
2. Use a piece of wire or metal sheet to replace the multimeter fuse. This may seem like a quick fix when you can't find a spare fuse on hand, but such fuses can pose serious security concerns.
3. Use of inappropriate tools for the work performed. It is important to use a DMM suitable for the job to be done. First, make sure that the DMM (or other test tool) has the correct CAT (electrical safety) rating for each test situation being performed, even if it is a day by switching to a different DMM; second, Make sure that the maximum continuous working voltage of the digital multimeter meets the actual test needs.
4. When using a multimeter to measure a live line, power off the line as much as possible. If it is necessary to measure live lines, be sure to use the correct insulating tools, wear ear protection, safety glasses, an arc shield, and insulating gloves, remove watches or other jewelry, stand on insulating mats, and wear flame retardant overalls (not normal work clothes).
5. Ignore the test leads. Test leads are an important aspect of keeping your digital multimeter safe. Make sure the test leads are also CAT rated for electrical safety for the job; and use test leads that have double insulation (silicone material), shielded input connectors, finger guards, and a non-slip surface.
6. Do not perform tests with both hands at the same time! One trick to keep in mind when measuring live lines: keep one hand in your pocket. This makes it difficult to form a closed circuit through the anterior chest and the heart. Hang or lower the multimeter whenever possible and avoid holding the multimeter in your hands to minimize the risk of exposure to transient voltages. Of course, in higher hazard measurements, additional measures should be taken to reduce the hazard and arc flashover risk. These additional measures include the use of protective equipment specified in the National Electrical Code (such as protective gloves, clothing, and goggles) to provide arc protection.
