A simplified draw of electrical connections of the instrument is shown in fig. 6.242 Permanent magnets provide the dramatics for both the generator & the ohm-meter.
The moving element of the ohm-meter consist of trine waves known as real (or deflecting) coil, jam (or apply) coil and compensating coil, which argon mounted rigidly to a pivoted central shaft and which argon free to rotate over a stationary C-shaped bid core.
The coils are connected to the circuit by means of elastic leads (or ligaments) that exert no restoring torque on the moving element. and so the moving element may take up whatever position over the scale when the generator handle is stationary.
The current (or deflection) coil is connected in series with the resistance R between one generator last-place and the test terminal marked L. The series resistance R protects the current (or deflecting) coil in case the test terminals are short-circuited and also control the range of the instrument.
The pressure (or control) coil in series with a compensating coil and protection resistance R is connected crossways the generator terminals. Compensating coil is provided to obtain better scale proportions and to see the instrument a static.
When the current from the generator flows finished pressure coil, the coil tends to set itself at right angles to the field of the persistent magnet. With the test terminals open, corresponding to infinite resistance, no current flows through deflecting coil.
The pressure coil thus governs the motion of the moving element, make it to move to its extreme counter-clockwise position. The point on the scale indicated by the pointer under this condition is marked infinite resistance.
accredited coil is wound to produce clockwise torque on the...If you want to get a full essay, order it on our website: Orderessay
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