Differences Between Gravity Control and Spring Control

Comparison of Gravity Control and Spring Control

Gravity control or Spring control both are comes under the category of "controlling torques" of an electrical measurement instrument.Before going have a comparison between gravity control and spring control let us have a look at why we need controlling torque in a measurement instrument?

1) Controlling torque produces a force equal and opposite to the deflecting force in order to make the deflection of pointer at a definite magnitude. If this system is absent then the pointer will swing beyond its final steady position for the given magnitude and deflection will become indefinite.

2) It brings the moving system back to zero position when the force which causes the movement of the moving system is removed. It will never come back to its zero position in the absence of controlling system. We have some advantages of spring control over gravity control.

Advantages of spring control | Disadvantages of gravity control

Gravity Control Spring Control
Adjustable small weight is used which produces
the controlling torque.
Two hair springs are used which exert controlling torque.
Controlling torque can be varied. Controlling torque is fixed.
The performance is not temperature dependent. The performance is temperature dependent.
The scale is nonuniform. The scale is uniform.
The controlling torque is proportional to sinA (A is angle). The controlling torque is proportional to 0.
The readings can not be taken accurately. The readings can be taken very accurately.
The system must be used in vertical position only. The system need not be necessarily in vertical position.
Proper levelling is required as gravity control. The levelling is not required.
Simple, cheap but delicate. Simple, rigid but costlier compared to gravity control.
Rarely used for indicating and portable instruments. Very popularly used in most of the instruments.

Controlling System: Gravity vs Spring Control
Advantages of spring control over gravity control
What is advantages of spring control over gravity control
What is gravity control,spring control?
Controlling torque in measuring instruments