A multimeter, also known as a tlectrical testers, circuit meter, or circuit multimeter, is a convenient measuring instrument that can measure voltage, resistance, and current with a single unit. They are used for various measurements during experiments and evaluations, and for maintenance and inspection of electrical equipment.
Although there are some differences depending on the industry or type of business, those with an analog meter display are often called "testers," or "analog multimeter" while those with a digital meter display are called "multimeters.
In addition, large-size meters that are used in a stationary position, such as on a desk, are sometimes distinguished as Digital MultiMeters(DMM).
There are several ways to call them, but the basic functions are the same.
- (1) Test probe(probe pen、test lead)
This is an input device for making contact with the part or parts to be measured and performing measurement.
- (2) Measurement terminal
Receives the signal input from the test probe. The position of the terminal where the test probe is inserted differs depending on the work to be measured.
- (3) Function switch (range switching switch)
Switches the measurement mode such as AC voltage, DC voltage, and current, and the range of measurement.
- (4) Function button (select button)
In the case of the digital multimeter, the function switch and function button are combined to switch the measurement mode. Press the function button to switch the LCD display.
- (5) Zero ohms adjuster knob
This knob is used to correct the display variation caused by internal resistance, etc.
- (6) Meter Scale
- (7) Meter pointer
- (8) Display board
Let's check the various measurement methods.
First, in the case of the analog multimeter, adjust the zero position of the multimeter as a preparation before measurement. Also, check the continuity. Set the range switch to the resistance measurement mode, and place the test lead pins against each other; if the value is close to 0Ω, it is OK.
(1) Basically, measurement with a multimeter is as follows
Insert the red plug of the test lead into the + input terminal and the black plug into the - input terminal.
(2) Adjust the measurement range.
(3) Touch the test pin to the measurement area.
(4) Check the scale that matches the measuring range of the switching knob from the meter scale, and read the numerical value indicated by the ammeter's pointer (in the case of a digital multimeter, read the numerical value from the display panel).
In this way, measurement is performed in four steps. Excessive current or voltage may cause a malfunction, so if the measurement value is unpredictable, start measurement from the maximum range in any mode, and then lower the range while observing the situation.
How to measure AC/DC voltage
After inserting the test lead into the terminals, switch the range knob to AC/DC voltage mode to select the expected voltage range. Then, place the black test probe on the "-" side of the measurement target and the red test probe on the "+" side.
How to measure resistance
After inserting the test lead into the terminals and switching the range switch knob to resistance mode, apply the test sticks to each other and turn the zero-ohm switch knob to set the pointer to the 0Ω position.
After alignment, place the red and black test pin on both ends of the measurement target. Be sure to turn off the power to the measurement object before taking the measurement.
How to measure DC current
After inserting the test lead into the terminals and switching the range switch to DC current mode, place the red test stick on the + side of the measurement target and the black test stick on the - side. Note that the analog multimeter cannot measure AC current.
There are two types of multimeters: analog and digital. As the whole world is becoming digitalized, digital multimeters are also becoming the mainstream, but both have their own merits and demerits.
Advantages of digital multimeters
- Because it displays numerical values, there is no variation among multimeters.
- The multimeter itself is highly accurate and can take accurate measurements.
- Various functions can be used by switching modes, such as temperature measurement mode using thermocouples and current-checking mode.
- Easier to operate than analog multimeters.
- Wide range of products.
Disadvantages of digital multimeters
- There are many functions, so it takes some getting used to.
- Difficult to read fluctuating values
- Cannot be measured without batteries
Advantages of analog multimeters
- Easy to understand by sense.
- Easy to recognize fluctuating values such as voltage and current because the needle can be shaken.
- Only voltage and current can be measured without batteries.
Disadvantages of analog multimeters
- There is variation due to internal resistance, resulting in measurement errors.
- It is necessary to read the scale.
Especially for digital multimeters, there are not only inexpensive handy type multimeters but also high performance multimeters with high price. They are safer, more durable, and more accurate than cheaper multimeters.
Other features include the ability to measure multiple channels at the same time, a wide range of currents and voltages, and the ability to connect via USB.