The correct application method and precautions for pointer type multimeter
Multimeters, also known as multimeters, triple meters, or multiplexers, are divided into pointer type multimeters and digital multimeters. It is a multifunctional and multi range measuring instrument. Generally, a multimeter can measure DC current, DC voltage, AC current, AC voltage, resistance, and audio level. Some can also measure AC current, capacitance, inductance, and some parameters of semiconductors
Method/Steps
Mechanical zeroing and Ohmic zeroing. To reduce measurement errors, mechanical zeroing should be performed before using a multimeter (usually only once during use). When using an ohmmeter to measure resistance, it is necessary to first perform an ohmic zero adjustment (i.e. electrical zero adjustment), which means short circuiting the two probes and adjusting the "zero ohm" adjustment knob to make the pointer of the multimeter reach the 0 ohm position on the right end. If the pointer cannot reach the 0 ohm position, it is usually caused by insufficient battery voltage in the meter. A new battery should be replaced before the measurement can be carried out. In the future, every time the range (gear) is changed, an ohmic zero adjustment must be performed.
During use, it is strictly prohibited to use an ohmmeter to measure the measured resistance when it is live. Otherwise, applying voltage can easily cause damage to the multimeter or cause unexpected circuit failures.
Correct wiring. Due to the fact that the DC meter head used by the multimeter only allows current to flow from the "+" pole to the "1" pole, the sockets and terminals on the multimeter panel have polarity markings. When using, connect the red probe to the "+" polarity socket and the black probe to the "1" polarity socket. When measuring DC voltage and DC current, it is important to note that the polarity of the positive and negative probes should not be reversed to prevent pointer reversal. If a pointer reversal is found, the probe should be immediately replaced. When measuring current, the instrument should be connected in series with IPP45N06S3L-13 in the tested circuit; When measuring voltage, the instrument should be connected in parallel at both ends of the tested circuit. When measuring transistors with a multimeter, it is important to remember that the red probe of the multimeter is connected to the negative terminal of the internal battery, and the black probe is connected to the positive terminal of the internal battery.
Choose the correct measurement gear. The measurement gear includes the measurement object and range. When measuring voltage, the conversion switch should be placed in the corresponding voltage range, and when measuring current, it should be placed in the corresponding current range. If the current gear is mistakenly used to measure voltage, it will cause damage to the instrument. When selecting the current or voltage range, the pointer should be at a position of more than 2/3 of the scale; When selecting the resistance range, make sure the pointer is in the middle position of the scale. The purpose of doing this is to minimize measurement errors as much as possible. When measuring, if the numerical range of the measured current and voltage cannot be determined, the conversion switch should be turned to the corresponding range first, and then gradually reduced to the appropriate range according to the degree of pointer deflection.
Read the table correctly. There are many scales on the dial of the multimeter, which are used for different measurement objects. Therefore, when measuring, it is necessary to read on the corresponding scale, and attention should be paid to the coordination between the scale reading and the range. That is, the "reading" on the scale line of the meter head cannot be confused with the "measured value". "Reading" refers to the value directly read from the scale line, while "measured value" represents the measured value represented by the reading, which is often obtained through conversion. Although sometimes the two are the same in value, in many cases they are different. In addition, when reading, the pointer and its projection on the reflector should also overlap to avoid measurement errors.
matters needing attention
When conducting high voltage measurements or when there is high voltage near the measurement point, be sure to pay attention to personal and instrument safety. When conducting high voltage and high current measurements, it is strictly prohibited to switch the range up and down when energized, otherwise it may damage the switching switch. In addition, after using the multimeter, it is best to place the conversion switch in neutral or the highest AC voltage position to prevent damage to the multimeter due to negligence during the next measurement.
After using the multimeter, do not rotate it on the resistance gear because there is a battery inside the meter to avoid accidentally short circuiting the two meter rods and consuming the battery. It is best to place the conversion switch in the high AC voltage gear or neutral gear.
