The multimeter is widely used in every measurement techniques. With the help of multimeter we can measure various quantities such as resistance, AC & DC voltage, current, capacitance etc. A multimeter is a voltmeter, ammeter, and millimeter combined together. There, it is also known as VOM (Volt-Ohm Millimeter). Multimeter may likewise have different capacities, for example, diode testing, coherence test, transistor test, TTL rationale test, and recurrence test.
There are two types of multimeter
- Analog Multimeter
- Digital multimeter
Analog multimeter has an analog display. This multimeter is work on the principle of Permanent Magnet Moving Coil (PMMC). PMMC has a deflecting pointer or needle which indicates the value of measured quantity on the printed scale, two permanent magnets which produce a strong magnetic field one soft iron core which moves between the permanent magnets. The pointer is mechanically connected with this moving core, so when the core will move the pointer will also move.
Analog multimeter has many ports of different values or range. Before starting of measurement with it inserts the probe in the reflected port.
When measuring the values of resistance, set the multimeter at zero position with the help of
Zero-Ohm Adjustment Knob.
Generally, two types of probes are used to measure any quantity – Red probe for positive voltage and Black probe for Negative voltage.
The printed scale is used behind the pointer because the user can easily read the values on multimeter display. This scale shows the range of voltage as well as resistance.
Digital multimeter has a digital display. This digital display is a Liquid Crystal Display (LCD). The display shows the values of the measured quantity in numerical values. This display is work on the principle of seven segment display. In the seven segment display, there is a total of seven displays are present and with the help of these seven displays any number between 0-9 can be displayed on the screen.
The digital multimeter has also two probes Red probe for positive voltage and Black probe for Negative voltage. Two jacks are present on the multimeter one is COM and second is positive jack. COM jack means Common jack and it is used to connect the black probe which is necessary for all measurement and tests. The positive jack marked with Voltage (V), Resistance (Ω) and Current (mA) and used to connect the Red probe.
The rotatory switch or sector is used to select the unit and range for the measurement and test. This knob is also used as an On/Off switch of a multimeter.
Digital Multimeter has a point of a continuity test, which is used for the testing of continuity between two terminal in electrical and electronics circuits.
- Be beyond any doubt the test leads and turning switch are in the right position for the ideal estimation.
- Never utilize the meter if the meter or the test drives look harmed.
- Never measure obstruction in a circuit when power is ON.
- Never connect the test probes to a voltage source when a test lead is connected to the 10 A or 300 mA input jack.
- To maintain a strategic distance from harm or damage.
- Never apply more than the prescribed voltage between any input and earth or ground terminals.
- Be watchful when working with voltages over 60 V DC or 30 V AC RMS. Such voltages represent a stun danger.
- Keep your fingers behind the finger guards during the test, when taking the measurement.
- Remove test probes from the circuit before replacing batteries or fuse.