The basic guts or the part that makes any analog panel meter work is referred to the meter movement.
There are several different types of meter movements. In this white paper, we are going to discuss how the meter movements work and the various types.
The meter movement itself is based on principles derived from D’Arsonval, a French Physicist in the nineteenth century.
A moving coil is located placed between two magnet assemblies. One small magnetic core that is placed inside the coil and another large magnet placed above the coil. The coil itself consists of very fine copper wire wound around an aluminum core. The wire can be as fine as a human hair in some cases and is wound on a custom machine that applies the correct tension on the wire. The number of turns or revolutions around the core itself is very important. As more wire is wrapped around the core the current capacity decreases and resistance increases (all things being equal). As current flows through the wound coil assembly from the source being measured a reaction occurs between the magnets. This electromagnetic field causes the coil to twist or push against the spring and the pointer to move to the right hand of the scale for most applications. Once the current is released, the spring relaxes and returns to zero. Believe it or not, the spring itself it part of the circuit as well. One end of spring is soldered to the zero adjust which in turn I connected to the negative terminal of the meter by the grey wire shown below. If you were to flip the movement over, you will see a spring on the back that is directly soldered to the positive terminal of the meter. Balancing the movement itself is the challenge in producing a meter that is uniform and meets specification across the range. There are many techniques used to balance meters, Hoyt typically uses tiny wound wire coils that are crimped on. They are positioned in the horizontal and vertical axis to the balance/cross arm. The various pointer types (airplane, lance, spade, etc.) are fastened to the balance/cross arm at the 12 O’clock position.
Hoyt White Paper Analog Panel Meter Basics - Movements, How Do They Work?
Hoyt Meter Video Analog Meter Basics and Movements
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