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Electro-dynamic tools

introduction

Measuring instruments shall be classified in accordance with the number of the device is measured and principle of operation.
Three general principles of work are:
The solenoid that uses magnetic effects of electric currents.
electrostatic, which uses the forces acting between electrically charged conductors.
èlektrotermičeskaâ, which uses the effect of warming up.
Electric measuring instruments and measuring devices are used to indicate directly the value of current, voltage, power, or energy.

Various forces/moments in measuring instruments

Deviating time/effort: flight of any instrument determined by joint deflective torque/force control of torque/force and damping time/effort. Torque variance should depend on the electrical signal is measured; This torque/force causes movement of the tool to rotate from its zero position.
Manage the time/effort: flight of any instrument determined by joint deflective torque/force control of torque/force and damping time/effort. Torque variance should depend on the electrical signal is measured; This torque/force causes movement of the tool to rotate from its zero position.
Damping torque damping force required:/to act in the direction opposite to the direction of motion of a mobile system. This brings the moving system at rest in decline position fast enough without any hesitation or very small fluctuations. This is ensured by the I) friction of air friction) liquid (II) (III)), the eddy currents. It should be noted that any braking force should not affect the steady state deflection obtained with this deflective force or torque. Damping force increases with the angular velocity of the mobile system, so its effect is greatest when the rotation is fast and zero, when the rotation system is equal to zero. Details of mathematical expressions for the above points are addressed in the description of the various types of tools.

Construction and the basic principle of Moving-iron instruments

This electromagnet type vehicle in which magnetism is not permanent.
Electromagnetic tools are classified as (I) with a moving iron instruments (II) electrodynamic or dynamometer instruments, (III) induction devices.
When moving-iron instruments float system consists of one or more pieces of specially-shaped soft iron, which swivel as the effects of the magnetic field generated by the current in the coil.
There are two main types of moving iron instruments, namely:-
Disgust (or double rail type).
Attraction (or one-iron) type

Tools type load cell

Electrodynamic type devices are similar to elements of the PMMC-type except that the magnet is replaced by two series-connected core coils that produce a magnetic field when voltage is applied.
Fixed coils are separated far enough apart to allow the passage of shaft movable coil.
Movable coil is a pointer, which is balanced by counterweights. Its rotation is controlled by the springs.
Engine torque is proportional to the product of the currents in movable and stationary coils. If the current is restored, the polarity and the polarity of the movable coil back at a time, and rotate effort continues in the original direction. Because reversing current direction does not reverse the rotation of forces, this type of devices can be used to measure AC or DC voltage, or a great use as measuring power wattmeter.