Electrostatic Instrument Working Principle – Advantages and Disadvantages

An electrostatic instrument is an instrument that works on the principle of attraction or repulsion of electrodes that carry electrical charges. It uses the static electric field to produce a deflecting torque and is used to measure high and low voltages as well as the power of a given circuit. It is a powerful tool for analyzing electrical circuits, as it can provide accurate readings of voltage and power in a given system. Additionally, the electrostatic instrument can be used in a wide range of applications, such as in industrial, medical, and scientific fields.

The electrostatic instrument is based on the principle of mechanical interaction between electrodes of opposite electrical charge. This interaction yields a measurable quantity, which is then converted into either an alternating current (AC) or direct current (DC) voltage. This voltage is used to detect, measure, and monitor changes in electrical charge. The instrument measures the charge that is present in the area, and then displays the result on a screen or other visual indicator. It is used in a number of applications, including measuring the strength of electric fields, determining the capacitance of a circuit, and detecting the presence of electrical charge on an object.
There are two methods of constructing electrostatic instruments.

• The electrostatic instrument stores charge by creating an electrostatic field between two oppositely charged plates, which attract one another and hold the maximum amount of energy.
• In this type of instrument, there is a force of attraction or repulsion between the rotating plates. Force and Torque Equations of Electrostatic Instruments

Linear Type Electrostatic Instrument

The linear electrostatic type instrument consists of two plates, A and B, which are charged with opposite polarities. Plate A is positively charged, while Plate B is negatively charged and connected to a spring, allowing it to move. The fixed positive plate A creates an electric field between the two plates, while the movable negative plate B provides a measure of the strength of the electric field. By adjusting the spring, the movement of the negative plate B can be controlled to determine the strength of the electric field.

When a voltage is applied to the two plates of a capacitor, an attractive force is generated between them, causing the plates to move closer together until the force reaches its maximum value. The amount of energy stored between the two plates is related to the capacitance (C) of the capacitor, which is measured in farads (F). The expression for the total energy stored between the plates is a function of the capacitance and the applied voltage.

Rotary type Electrostatic Instrument

This type of instrument uses rotary plates to generate an electromagnetic force. As the rotary plates move, they create a magnetic field which causes either an attraction or repulsion between them. This force can then be used to measure or control a variety of physical phenomena.

Advantages of Electrostatic Instrument

1. The electrostatic instrument can be used to measure both AC and DC voltages.
2. The electrostatic instrument uses very little power.
3. The level of high voltage can be determined using an appropriate measuring instrument.
4. In a rotary type electrostatic instrument, angular displacement occurs between the fixed and the moving plates, even though linear displacement is present.
5. The instrument has reduced waveform and frequency errors.
6. No errors occur due to stray magnetic fields.
7. This instrument is designed to measure high voltages.

Disadvantages of Electrostatic type instrument

1. The instrument utilizes a non-uniform scale.
2. The instrument involves a force of very low magnitude.
3. The cost of this instrument is significantly higher than other instruments.
4. The instrument is very sizable.