Multimeter & Voltmeter ( simple guide)

 Multimeters :

 A device used to measure electrical quantities. A typical multimeter can measure alternating- and

direct-current potential differences (voltages), current, and resistance,

with each quantity having several full-scale ranges. It is a logical development of the electrical meter,

providing a general-purpose instrument. It is also known as a volt-ohm meter (VOM).

Many different types of special-purpose multimeters are produced to meet the needs of specialists

such as telephone engineers and automobile mechanics who test ignition circuits.

A multimeter can be a hand-held device for basic fault finding and field service work, or it can be

a bench instrument with extremely high accuracy.

They can be used to diagnose electrical problems in a variety of industrial and household devices,

including electronic equipment, motor controls, domestic appliances, power supplies, and

wiring systems.

Analogue multimeters:

An analogue multimeter is a type of permanent magnet moving coil (PMMC) meter.

It operates on the d'Arsonval galvanometer principle. The analogue multimeter has an analogue display

that indicates the level of measurement being made by the deflection of a pointer on the scale. As the

measuring quantity increases, the pointer deviates from its initial position more and more.

Working of Analogue multimeters:

Because the analogue multimeter is a PMMC type instrument, when a current is passed through its coil, the coil moves in a magnetic field produced by the permanent magnet. A pointer is connected to the coil. When current flows through the coil, a deflecting torque acts on the coil, causing it to rotate by an angle, causing the pointer to move across a scale. To provide the controlling torque, a pair of hairsprings is attached to the spindle.

Digital multimeter:

A digital multimeter, or DMM, is one of the most commonly used pieces of test equipment today; they are practically indispensable in any electronics laboratory, for both the home, hobbyist, and professional electronics engineer.

Working of digital multimeter:

DMMs, or digital multimeters, can measure a wide range of parameters within an electrical circuit. Basic DMMs can measure amps, volts, and ohms, just like older analogue metres, but due to the ease of incorporating additional functionality into an integrated circuit, many digital multimeters can also make a variety of other measurements.

Many of them include functions for measuring capacitance, frequency, continuity (with a buzzer to aid in easy measurements when inspecting the circuit board), temperature, transistor functionality, and frequently a variety of other measurements.

Voltmeter:

A volt metre, also known as a voltage meter, is a device that measures the voltage or potential difference between two points in an electronic or electrical circuit. The voltmeter is typically used for Alternating Current (AC) or Direct Current (DC) circuits. Radio Frequency (RF) voltage can also be measured using specialized voltmeters.

A voltmeter measures voltage in volts, millivolts (0.001 volt), or kilovolts (1,000 volts). A voltmeter is connected in parallel to a device to measure its voltage. This configuration is critical because objects in parallel typically experience the same potential difference. It is connected in parallel with the circuit because it experiences the same voltage drop.

A voltmeter has a high internal resistance as well. This is done primarily to measure the potential difference between the two points of the circuit. As a result, the measuring device's current remains constant. In other words, the voltmeter's high resistance will obstruct the flow of current through it. This enables the device to take accurate voltage readings.

Analog voltmeter: 

An analogue voltmeter is primarily used to measure alternating current voltage.

The reading is displayed using a pointer that is fixed on a calibrated scale.

The torque acting on the pointer has an effect on its movement.

The magnitude of the torque produced is proportional to the voltage being measured.

Digital voltmeter:

A digital voltmeter (DVM) measures an unknown input voltage by converting

it to a digital value and displaying it numerically.

DVMs are typically built around a type of analogue-to-digital converter known as an integrating

converter.

The accuracy of the DVM is affected by a variety of factors, including input impedance,

temperature, and power supply voltage variations.

The input resistance of the least expensive DVMs is around 10 M.

For low voltage ranges, the input resistances for precision DVMs of 1 G or higher (below 20 V).

To ensure that the manufacturer's specified tolerances are met,

the DVM must be calibrated on a regular basis with a voltage standard such as the Weston Cell.