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Temp gauge accuracy

5K views 4 replies 2 participants last post by  cypress188 
#1 ·
I got this from a peachpart member.

The 100C mark is Factory Test Indicator mark used in testing procedure of both gauge and sensor for specification accuracy.
The sensor/gauge test procedure is to sub. a 38 ohm resistance in place of the sensor. The gauge will then align with the 100C indicator marking.
I used two 82 ohms in parallel, resultant resistance is 41ohms. I say it's pretty close & my gauge is accurate. :thumbsup:
 

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#2 · (Edited)
What tolerance were your resistors? At 10%, your range could be anywhere between 36.9 and 45.1 ohms. (Stastically with 2, tolerance is cut in half to 5%). Best to use a Digital Multi Meter to measure the values. Don't forget to subtract probe resistance.

Otherwise, I recommend testing with 1% tolerance resistors:
38.3 = 37.9 ~ 38.7 ohms
10.0 + 28.0 series = 37.8 ~ 38.2 ohms
12.7 + 12.7 + 12.7 series = 38.0 ~ 38.2 ohms

Next project: improve fuel guage accuracy, and compensate for the bottom 5cm which the float cannot detect, and MB conveniently calls a "reserve" (beacuse their engineers can't figure out how to measure all the way to the bottom of the tank).
 
#3 · (Edited)
Hehe, I just did it for curiosity sake. Gauge is not out of whack, I'm happy. :D

But now that I looked at the resistor(s) I used, I am confused.

DMM shows 82.5 ohms (single resistor)
DMM shows 41.5 ohms (2 resistor in parallel)

How can a 5 band resistor "grey-red-black-red-white" = 82 ohms?
According to those colors, it = 82K ohms.
Also "white" is not a tolerance?
 
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