52 mm diameter.
The temperature indicator applies the resistance measurement principle. A sensor containing a resistor with strong temperature dependence (PTC) converts the temperature of the fluid to a corresponding resistance value.
A turning magnet ratio measuring movement measures this resistance value. This value is displayed by a pointer moving over a dial graduated in temperature units. The turning magnet movement for ratio indication comprises three stationary coils wound at 90
against each other, and a rotating permanent magnet disk in these coils. The coils are connected to determine a ratio, so that the instrument is insensitive to on-board voltage fluctuations.
This means that the pointer travel is only determined by the magnitude of the current flowing through the measuring system.
A magnetic shield prevents effects of external magnetic fields, indication errors due to temperature changes are corrected by a compensating resistor. A dropping resistor is used to adapt the measuring movement to higher operating voltages (e.g. 24V).