Voltage Limiter (Constant Voltage) Gauge Operation

The voltage limiter type indicator gauge is a bi-metal resistance type system consisting of a voltage limiter, an indicator gauge, and a variable resistance sending unit. Current to the system is applied to the gauge terminals by the voltage limiter, which maintains an average pulsating value of 5 volts.
The indicator gauge consists of a pointer which is attached to a wire-wound bi-metal strip. Current passing through the coil heats the bi-metal strip, causing the pointer to move. As more current passes through the coil, heat increases, moving the pointer farther.
The circuit is completed through a sending unit which contains a variable resistor. When resistance is high, less current is allowed to pass through the gauge, and the pointer moves very little. As resistance decreases due to changing conditions in system being monitored, current increases through the gauge coil, causing pointer to move farther.