Oil Temp Gauge Revisited, 200c temp sensor resistance vs temperature Options

[Superhawk996]

I think most people are familiar with the Panorama calibration graphics.



What I haven’t been able to find is the actual calibration curve for the 200C temp sensor that goes into the taco plate.

So . . . I went and got the data in an effort to help @ron914 troubleshoot his misbehaving oil temp gauge.

Oil was heated and a Fluke thermocouple meter was used to read oil temp. The resistance of the 200C sensor was measured both while heating and then on the cool down to get the hysteresis.

The pictures I’m going to attach later in this thread were done with a late oil temp gauge. The gauge I used pretty much matched the Panorama calibration graphics.

Here is the chart


Here is the raw data.

[Rusty_Rivets]

Superhawk, when you did your tests, did you start heating the oil and then take readings throughout the heating process, and then again during the cooling process rather than letting the oil reach a stable temperature for each measurement? The reason I ask is because the difference in readings between heating and cooling look to me to be a time lag effect rather than hysteresis. (I think VDO would have to put a lot of effort into making a sensor with hysteresis that awful. (IMG:style_emoticons/default/smile.gif) ) It looks to me like the thermal mass of the VDO sending unit is greater than the thermal mass of the Fluke temperature sensor. So, by the time the VDO sensor has heated to a certain temperature, the surrounding oil bath is already hotter (or colder if cooling).