Gday guys,

As i will be looking into doing calibration checks on automotive instruments in the future. I wanted to know some details on most the devices on the market.

Firstly on Temperature gauges. These usually comprise of a Element & a gauge with electronics.

For example
* probe reacts with temperature
* Probe transmits a signal to the gauge
* gauge interprets that signal and displays a reading.

Firstly what type of temperature element is used in most aftermarket oil & water temp instruments ? They usually always seem to be of a 2wire design but does not look like a thermocouple - so would it be a type of RTD or thermistor?

Secondly what type of signal is usually transmitted to the gauge from the probe? mv, ma, resistance change etc

Thanks everyone

Lyle

 

I cannot speak for the aftermarket,but most if not all OEM temp gauges are negative coefficient type. (NTC) The signal is a change in resistance.

 

I thought as much. Is the Upper and lower ranges of resistance usually the same? or is it range specific as well?

eg 0 - 100deg = 0 - 100ohm, 0 - 200deg = 0 - 100ohm

OR

eg 0 - 100deg = 0 - 100ohm, 0 - 200deg = 0 - 200ohm

Does that make any sense?