Hello everyone, I am Rose. Today I will introduce a multimeter to you. A multimeter is an instrument that integrates a range of regularly used electrical measurement capabilities, and it is one of the most commonly used measuring devices for electronic enthusiasts.

Ⅰ. What is a multimeter?

Multiplex meters,  multimeter, three-meters, multi-meters, and more names for multimeters exist. In power electronics and other industries, they are essential measuring tools. The main purpose of these instruments is to measure voltage, current, and resistance. Multimeters are classified as pointer multimeters or digital multimeters based on their display method. It's a multi-purpose, multi-range measuring device. Multimeters are used to measure  DC  current,  DC voltage,  AC  current,  AC voltage, resistance, and audio level, among other things. AC current, capacitance, inductance, and semiconductor characteristics are all measured by some.

Ⅱ. What is the composition of a multimeter?

The meter head, the measurement circuit, and the change-over switch are the three basic components of the multimeter,  The most basic tool in the field of electronic testing is the multimeter.  which is also the most extensively used testing instrument. Multimeters are also known as multimeters, three-meters (current, voltage, and resistance are used in three different ways), multiplex meters, and multimeters. Pointer and digital multimeters are the two types of multimeters. There's even one with oscilloscope capabilities. An oscilloscope multimeter is a measurement tool with multiple functions and ranges. Multimeters can be used to measure DC current, DC voltage, AC voltage, resistance, and audio level, among other things. Some can also detect AC current, capacitance, inductance, temperature, and a few semiconductor characteristics (diodes, triodes). Analog meters have been phased out in favor of digital multimeters. Digital instruments have higher sensitivity, precision, clear display, robust overload capacity, are easier to carry, and are more convenient and simple to operate than analog instruments.

Header

The multimeter's head is a sensitive ammeter. A variety of symbols, scale lines, and values are displayed on the dial on the meter head. This electric meter is a  multimeter that can measure current, voltage, and resistance, as shown by the sign A-V-. Multiple scale lines are printed on the dial, with the resistance scale line marked with "at the right end, zero at the right end, and 0 at the left end. The value distribution on the scale is unbalanced. "-" or "DC" denotes direct current, "or "AC" denotes alternating current, and "denotes the scale line that both AC and DC share. The scale values corresponding to the different gear settings of the selector switch are shown by the lines of numbers beneath the scale line.

On the meter head, there is also a mechanical zero adjustment knob for correcting the pointer's zero position at the left end.

switch

The multimeter's selector switch is a multi-position rotary switch. To pick measurement items and ranges, use this tool. "mA" denotes DC current, "V (-)" denotes DC voltage, "V ()" denotes AC voltage, and "denotes resistance. Each measurement item is separated into numerous ranges from which to choose.

Test lead and test lead socket

There are two types of test leads: red and black. Insert the red test lead into the jack labeled "+" and the black test leads into the jack labeled "-" when using.

Meter head (pointer type)

It's a magnetoelectric DC ammeter with high sensitivity. The meter head's performance is essentially what determines the multimeter's main performance index. The meter head's sensitivity relates to the value of direct current flowing through the meter head when the pointer is fully deflected; the smaller the value, the higher the meter head's sensitivity. When measuring voltage, the higher the internal resistance, the better the results. On the meter head, there are four scale lines. Their responsibilities are as follows: The first (from top to bottom) is denoted by the letters R or, which denotes the resistance value. This scale line is read when the switch is set to ohms. The values of AC, DC voltage and DC current are indicated on the second line by the symbols and VA. This scale is read String when the switch is set to AC, DC voltage, or DC current, and the range is set to anything other than AC 10V. The third line is inscribed with a 10V symbol, indicating a 10V AC voltage. This scale line is read when the switch is in the AC or DC voltage range and the range is AC 10V. The audio level is indicated by the fourth bar, which is labeled with dB.

Meter head (digital)

A digital multimeter's meter head is typically made up of an A/D (analog/digital) converter chip, peripheral components, and a liquid crystal display. The meter head has an impact on the multimeter's accuracy. The number converted from the A/D chip is what the multimeter is commonly referred to as. For multimeters with three and a half digits, four and a half digits, and so forth. ICL7106 (3 and a half LCD manual range classic chip; subsequent versions include 7106A, 7106B, 7206, 7240, and so on), ICL7129 (4 and a half LCD manual range classic chip), and ICL7107 (4 and a half LCD manual range classic chip) are the most often used chips (3 and a half LED manual range Classic chip).

Measuring circuit

The measuring circuit is a circuit that converts numerous measurements into a little DC current that can be measured using a meter. Resistors, semiconductor components, and batteries make up the device.

After a series of processing, it can even transform variously measured (such as current, voltage, resistance, and so on) and varied ranges into a set number of small DC currents (such as rectification, shunting, voltage division, etc.) Measuring is done with the meter.

Changeover switch

Its purpose is to choose from a number of different measuring circuits in order to suit the measurement needs of various types and ranges. In most cases, the change-over switch is a circular dial with functions and ranges marked all around it.

Ⅲ. What's the role of a multimeter?

Voltage, current, and resistance are the three basic test components.

Measure capacitance, inductance, frequency, duty cycle, temperature, and transistor magnification to expand empty energy.

Ⅳ. What's the classification and principle of a multimeter?

Analog and digital multimeters are two types of multimeters that are commonly used. The pointer multimeter is a multi-function measuring equipment with a meter head at its heart, with the measured value read by the meter head's pointer. The digital multimeter's measured value is presented in digital form on an easy-to-read LCD screen, and some models also feature a voice prompt option. A multimeter is a type of meter that includes a voltmeter, an ammeter, and an ohmmeter.

Multimeter principle

The essential premise of a multimeter is that the meter head is a sensitive magnetoelectric DC ammeter (microammeter). There will be a current indication when a modest current passes through the meter head. However, because the meter head is unable to pass huge currents, some parallel and series resistors must be connected to the meter head to shunt or step down the current, voltage, and resistance in the circuit.

Ⅴ. Multimeter purchase skills

1. The display digits and precision of the multimeter

The most fundamental and significant indicators of a multimeter are the display digits and accuracy. In general, the greater the multimeter's display digits, the higher the accuracy, and vice versa.

2. Multimeter measurement method and AC frequency response

The multimeter's measurement method is mostly used to measure AC signals. Various frequency responses arise as the frequency of the AC signal changes, affecting the multimeter's measurement. When using a multimeter to test AC signals, there are two options: average value and real effective value measurement.

3. Function and measuring range

Manufacturers will create distinct functional measurement ranges for different multimeters. Ordinary multimeters can measure AC and DC voltage, current, resistance, and continuity, among other things, however, some multimeters lack a current function to save money.

4. Measurement stability and protection

Multimeters that are well-made are particularly self-protective. When you plug in the wrong lead wire, for example, some multimeters will automatically create a buzzer alarm... When purchasing a multimeter.  don't go for the cheapest option; instead, go for something that is practical and easy to use.

Ⅵ. How to use a multimeter?

1. Before using the multimeter.  become familiar with its capabilities and accurately pick the gear position, range, and meter pen jack based on the object to be measured.

2. If the amount of the measured data is unknown, set the range switch to the maximum value first, then move from the big to the small range until the meter's pointer indicates at least 1/2 of the full scale.

3. When measuring resistance, touch the two-meter pens to make the pointer point to the zero position after selecting the proper magnification gear. Adjust the "Zero" knob to reset the pointer to zero if it deviates from the zero position to ensure accurate measurement results. It should be checked as soon as possible if zero adjustments are not achievable or if the digital display issues a low voltage alarm.

4. When measuring the resistance of a circuit, the circuit's power source must be turned off, and no live measurements are permitted.

5. Pay attention to the safety of personal and instrument equipment when using a multimeter to measure. To ensure precise measurement and avoid dangers such as electric shock and instrument burning, do not touch the metal section of the test pen with your hands during the test. Instead, flip the position switch with electricity.

Ⅶ. Maintenance and repairment of multimeter

Multimeter maintenance

1. Do not connect to a DC voltage of more than 1000 volts or an AC RMS voltage of more than 700 volts.

2. When the function switch is in the and position, do not connect the power source.

3. If the battery is not installed or the rear cover is not fastened, do not use this watch.

Multimeter repairment

1. Visual inspection

You can feel the temperature rise of the battery, resistor, transistor, and integrated block if you find disconnection, desoldering, short circuit, fuse tube broke, burned components, and so on. The circuit diagram can help you figure out what's causing the unusual temperature rise.

2. Voltage measurement method

Check each important point's working voltage to see if it's normal, so the defect may be located fast. For example, measuring the A/D converter's working voltage and the reference voltage.

3. Short circuit method

In the procedure of verifying A/D converters, the short-circuit method is commonly utilized. When mending weak current and micro-electric equipment, this procedure is frequently utilized.

4. Open circuit method

Disconnect the suspect component from the machine's or unit's entire circuit. If the problem goes away, it's because it's in the disconnected circuit. This strategy is best used in situations where there is a short circuit in the circuit.

5. Measuring element method

The issue can be measured online or offline once it has been narrowed down to a specific location or set of components. Replace it with a good component if necessary. The component is broken if the fault disappears.