In electrical engineering, there are so many instruments used to measure various electrical quantities like voltage, current, resistance, frequency, and power. In this experiment, we shall study how to measure electrical quantities like voltage, current, and power.

Voltmeter:

A voltmeter is an electrical instrument that is used to measure the potential difference between two points in an electric circuit. A voltmeter is always connected in parallel with the circuit. It consists of a potential coil having a large number of turns that’s why the resistance of voltmeters is always in KΩ and MΩ. Voltmeter itself takes very minor current due to their high resistance that’s why their current is always negligible. Voltmeters consist of a calibrated scale, a pointer that moves on the calibrated scale, and a selector switch. The maximum selector value tells us the maximum measurable voltage values with the instrument. These meters can be horizontal, vertical, or slope types available for both AC and DC circuits. These voltmeters are available in different ranges and shapes in the market.

There are two types of voltmeters, one of them is analog and the other is digital. Analog meters are indicating type instruments that measure the root mean square value of the measured electrical quantity. The digital type voltmeter displays the measured value in the form of digits.

Ammeter:

Ammeter is an electrical instrument that is used to measure the flow of electric current in the circuit. Ammeters are instruments that are always connected in series with the load. Ammeter consists of a current coil of very few turns of thick copper wire which have a minimal value of resistance. It also consists of calibrated scale, a pointer that moves on the calibrated scale, and selector switches. Maximum selector switch value tells us the maximum measurable value of current which the ammeter can measure. These meters are available for horizontal, slope, and vertical use for both AC and DC circuits. Ammeters are available in different ranges and shapes in the market.

There are two types of ammeters, one of them is analog and the other is digital. Analog meters are indicating type instruments that measure the root mean square value of the measured electrical quantity. The digital type voltmeter displays the measured values in the form of digits.

Wattmeter:

A wattmeter is used to measure the power consumption of the electric circuit. Wattmeter consists of a current coil and voltage coil. The current coils are always connected in series with the load similar to the ammeter and voltmeter coil always connected in parallel with the load whose power is required to be measured. The wattmeter is indicating the type instrument consists of calibrated scale, a pointer or needle, and a voltage selector switch. These instruments are capable of measuring power for both AC and DC circuits. Wattmeters are also classified according to their position horizontal, slope, and vertical types.

Electrical Meters

Measurement of Power by Voltmer-Ammeter & Wattmeter

Take the Following Apparatus from the Electrical Store or Laboratory

Voltmeter ————————1

Ammeter ————————-1

Wattmeter ———————–1

Rheostat ————————–1

Auto-Transformer ————–1

Connection Leads —————10

Using Voltmeter & Ampere Meter

Circuit Diagram

Power Measurement  by Voltmeter & Ampere Meter

Procedure

  1. Issue the apparatus from the store and connect the apparatus according to the circuit diagram.
  2. Change the selector switches of the ammeter and voltmeter according to the supply input.
  3.  Correct the zero errors or pointer errors of the meter.
  4. Select the Rheostat value at 50% dial Value.
  5. Ask the instructor to check the circuit according to the circuit diagram.
  6. After checking the circuit, get permisssion form the Instructor to energize the circuit.
  7. Take readings of voltmeters and ammeters by varying autotransformers and rheostat respectively.
  8. After taking the readings, record the readings in the observation table and ask the Instructor to verify the taken reading.
  9. After Verification of the taken readings, switch off the power supply.

Observation Table

Observation Table 1

Using Wattmeter

Circuit Diagram

Wattmeter

Procedure

  1. Get issu the apparatus from the store and I connect the apparatus according to the circuit diagram.
  2.  Change the selector switch of wattmeter.
  3.  Correct the zero errors or pointer errors of the meter.
  4.  Select the Rheostat value at 50% dial Value.
  5.  Ask the instructor to check the circuit according to the circuit diagram.
  6.  After checking the circuit, energize the circuit.
  7.  Take readings of wattmeter by varying rheostat.
  8.  Record the readings in the observation table and ask theinstructor to verify the taken reading.
  9.  After Verification of the taken readings, Switch off the power supply.

Observation Table

Observation Table 2

Precautions:

  1. Handle the meters with great care because meters have many delicate parts.
  2. Connection must be tight, neat and clean.
  3. Always take readings after correcting the zero or meter error.
  4. Selector of the meters must be according to the supply range.
  5. Always energizes the circuit after getting permission from instructor.
  6. During experiment, care should be taken into account from electric shock.