This is the second article based on the electrical instruments- classification of electrical measuring instruments.
Before this article, I have shared electrical measurements and instrumentation covering all different instruments and their uses.
Electrical measurement quantities are used for the analysis and to check the performance of the electrical devices. These instruments are available in analog or digital form.
Mostly, analog meters are used in the electrical laboratory for practical studies and digital meters are used in commercial, industrial and various other purposes.
Electrical measuring instruments can be classified into different types.
Classification of Electrical Measuring Instruments
Here is a block diagram of the Electrical Instrument Classification.
Let’s see the description of each classified electrical measuring instruments, one-by-one.
Classification according to the Electrical Quantity
As per the Electrical Quantities, instruments are broadly classified into two parts.
- Absolute Instruments
- Secondary Instruments
1. Absolute Instruments:
These instruments give the value of the electrical quantity to measure in terms of the constant and its deflection. These instruments are known as ‘Absolute Instruments’.
It is also called as Primary Instruments or Indirect Instruments. These instruments are not required to compare with the standard values.
Example: Tangent Galvanometer is the best example of an absolute instrument.
These types of instruments are rarely used for commercial purposes.
2. Secondary Instruments:
These instruments give the value of the quantity to be measured directly into the deflection. These instruments are known as ‘Secondary Instruments’.
It is also called as Direct Instruments.
These instrument values are required to compare with absolute instruments or standard value of the instruments.
The secondary instruments are classified into two part,
- Deflection Instruments
- Null Deflection Instruments
Example: Ammeter, Voltameter, Wattmeter, etc are the example of the secondary instruments.
Classification according to the Nature of the Operation
The instruments can also be classified based on the nature of the operation. They majorly fall into the secondary instruments.
These instruments are divided into four major parts.
- Indicating Instruments
- Recording Instruments
- Integrating Instruments
- Null Deflection instruments
Shortly describe as,
1. Indicating Instruments:
The Indicating Instruments displays only the value of the electrical quantities at per time of measurements.
These instruments give the reading only when connected to the electrical supply. Otherwise, it goes to zero position.
Example: Ammeters, Voltmeters, Wattmeters, etc are the example of the indicating instruments.
2. Recording Instruments:
The Recording Instruments displays and records the reading of the electrical quantities at per time of measurements.
These instruments are generally used in the Generating Station and Substation.
Example: ECG, X-Rays are examples of the recording instruments.
3. Integrating Instruments:
The Integrating Instruments displays, record and add the numerical value of the reading of the electrical quantities at per time of measurements.
Example: Energy Meter, Ampere-Hour Meter are examples of the integrating instruments.
4. Null Deflection Instruments:
The Null Deflection Instruments show the reading of the electrical quantities without the deflection angle at per time of measurements.
Example: The ‘Potentiometer’ is an example of the null deflection instruments.
Classification according to the Electrical Supply
This classification is based on the AC (Alternate Current) and DC (Direct Current) types of the electrical supply.
- AC Instruments
- DC Instruments
1. AC Instruments:
The AC Instruments are connected with the AC supply. Further, they are classified into two parts…
- Single phase AC Instruments
- Three phase AC Instruments
Example: Moving Instruments [M.I.], Induction Instruments, Electrostatic Instruments, dynamometer Instruments, Electrostatic Instruments are the examples of the AC Instruments.
2. DC Instruments:
These instruments are connected with the DC supply.
Example: ‘Permanent Magnet Moving Coil Instruments’ is the best example of the DC instruments.
Classification of Electrical Measuring Instruments according to the Effect
Due to the various magnetic effects, electromagnetic induction effects, electrostatic effects, thermal effects, chemical effects, etc., there are more chances to get the application or system damaged.
So, the multiple types of instruments are used to measure and compare the unknown quantities with the standard value. These instruments protect the device.
The classification is as follows.
- Moving Coil Instruments
- Moving Iron Instruments
- Induction Instruments
- Electrostatic Instruments
- Electrolytic Instruments
- Hot Wire Instruments
Classification according to Moving Coil [M.C.] Instruments
The Moving Coil Instruments are classified into two parts.
- Permanent Magnet Moving Coil [PMMC] instruments
- Electrodynamic 0r Dynamometer types instruments
Classification according to Moving Iron [M.I.] Instruments
The Moving Iron Instruments are classified into two parts.
- Attraction type M.I. instruments
- Repulsion type M.I. instruments
Classification according to an Electrical Application
In daily routine, multiple instruments are used for multiple purposes. Instruments work on AC or DC electrical supply as per the appliances use.
Here is the list of the most popular and widely used instruments.
- LCR meter
- Frequency meter
- Capacitance meter
- Power factor meter
- Ampere-hour meter
- Live leakage detector
- Earth leakage detector
- Phase sequence detector
- Insulation fault detecting instrument
- Megger, etc.
These instruments are used in commercial, industrial, practically and many more purposes. They are manufactured by the topmost electrical companies.
There is also one more type of instrument called a multimeter.
What is a Multimeter?
Multimeters are a popular type of electrical measuring instruments. As per its name, it works like ammeters, ohmmeters, and voltmeters. It can measure the current, voltage as well as resistance.
Multimeters are available in Analog and Digital types.
Similarly, the LCR meter measures the inductance (L), capacitance (C), resistance (R).
Nowadays, these measuring instruments are mostly used.
From this study, we conclude that measurements and instruments are the most essential term in electrical, electronics, mechanical and other related fields. These instrumentations work as protective devices.
That’s all about the classification of electrical measuring instruments!
See you soon in the next article…
Thanks for Reading!
Myself Dipali Chaudhari. I am a master in Electrical Power System. Sharing my knowledge on this blog makes me happy. Apart from that, I love playing badminton. And sometimes I dwell on the Python programming.