Null Type vs Deflecting Type Instruments

Null Type Instruments:

A null type instrument is an instrument that works on the null deflection principle. In this type of instrument, a balance is achieved between the unknown quantity and a known quantity. When the balance is achieved, the instrument indicates zero, and the unknown quantity can be calculated. Examples of null type instruments are a potentiometer, Wheatstone bridge, and resonance galvanometer.

Deflecting Type Instruments:

A deflecting type instrument is an instrument that works on the principle of deflection. In this type of instrument, the unknown quantity is measured by the deflection produced by the quantity on a pointer or a scale. Examples of deflecting type instruments are a moving coil, moving iron, and electrostatic voltmeter.

Accuracy and Sensitivity:

Accuracy is the degree of conformity of an instrument's reading to the true value of the quantity being measured. Sensitivity is the degree of change that an instrument can detect in the quantity being measured. The higher the sensitivity of an instrument, the smaller the change it can detect.

Comparison:

When comparing null type instruments to deflecting type instruments, it can be concluded that null type instruments have higher accuracy than deflecting type instruments. This is because null type instruments work on the principle of balance, ensuring that the reading is as accurate as possible. On the other hand, deflecting type instruments are prone to errors due to friction, hysteresis, and other factors that can affect the accuracy of the reading.

However, it should be noted that deflecting type instruments have higher sensitivity than null type instruments. This is because deflecting type instruments can detect very small changes in the quantity being measured, while null type instruments require a significant change to produce a balance.

Responsiveness:

Responsiveness is the ability of an instrument to respond quickly to changes in the quantity being measured. When it comes to responsiveness, null type instruments are faster than deflecting type instruments. This is because null type instruments can achieve a balance quickly, while deflecting type instruments require time for the pointer to settle to a new position.

Conclusion:

In conclusion, null type instruments have higher accuracy and faster responsiveness than deflecting type instruments. However, deflecting type instruments have higher sensitivity than null type instruments. It is essential to choose the appropriate type of instrument depending on the application and the required accuracy, sensitivity, and responsiveness.