All analogue electrical indicating instruments need 3 essential devices these devices are briefly discussed below:
1- A deflecting or operating device.
A mechanical force is generated by the current or voltage which causes the pointer to have some deflecition from its 0 position.
2- A controlling device.
The controlling force works in opposition to the deflecting force & ensures that the deflection being shown on the meter is always the same for a given measured quantity. It also pr events the pointer always going to maximum level of deflection. There are 2 main types of controlling devices, which includes spring control & gravity control.
3- A damping device.
The damping force ensures that the pointer comes to rest state in its final position expeditiously & without undue oscillation. There are 3 main types of damping used
There are basically two types of scale — linear and non-linear.
A linear scale is shown in diagram (a) below, where the divisions or graduations are evenly spaced. The volt-meter shown has a range from 0 to100V, i.e. it has a full-scale deflection (f.s.d.) of 100V. A non-linear scale is shown in diagram(b) below. The scale is cramped at the beginning
1- A deflecting or operating device.
A mechanical force is generated by the current or voltage which causes the pointer to have some deflecition from its 0 position.
2- A controlling device.
The controlling force works in opposition to the deflecting force & ensures that the deflection being shown on the meter is always the same for a given measured quantity. It also pr events the pointer always going to maximum level of deflection. There are 2 main types of controlling devices, which includes spring control & gravity control.
3- A damping device.
The damping force ensures that the pointer comes to rest state in its final position expeditiously & without undue oscillation. There are 3 main types of damping used
- eddy-current damping,
- air-friction damping and
- fluid-friction damping.
There are basically two types of scale — linear and non-linear.
A linear scale is shown in diagram (a) below, where the divisions or graduations are evenly spaced. The volt-meter shown has a range from 0 to100V, i.e. it has a full-scale deflection (f.s.d.) of 100V. A non-linear scale is shown in diagram(b) below. The scale is cramped at the beginning
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