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Re: Temp sender resitance

Posted: Mon Oct 09, 2017 6:27 pm
by Galileo
Almost matches a table in an MG book I have:

Cold 222Ω
1/4 105Ω
1/2 65Ω
3/4 35Ω
Hot 20Ω

Which incidentally states that the fuel and temperature gauges are identical internally, not seen that ever said before.

The sender I've used is 287Ω at 40°C to 39Ω at 100°C with a switch at 96°C.

Edit as I'm wondering just what actual temperature is 'Normal' supposed to be anyway?!

Edit my edit because the internet says 90°C, which I knew anyway and I'm now just being silly, I'll get my coat.

Re: Temp sender resitance

Posted: Mon Oct 09, 2017 6:29 pm
by GrahamFountain
WRT the none linearities in the above values, if you plot the currents against readings, the voltage set are spot on linear, and the resistance readings aren't that far off (assuming a 10v ref and little to no resistance from the meter coil). That's exactly what I'd expect, given the guage will be, as they all are, an ammeter.

Graham

Re: Temp sender resitance

Posted: Mon Oct 09, 2017 8:21 pm
by GrahamFountain
Some rough mucking about with the numbers suggests the resistance of the guage is about 60-65 ohms, at which point the meter values against current caculated from the resistance and 10 volts supply straighten out nicely. And full scale deflection is about 115 to 120 mA.

Graham

Re: Temp sender resitance

Posted: Mon Oct 09, 2017 11:26 pm
by GrahamFountain
Looking at those numbers, it appears there's no chance of upping the reference voltage enough to get the sensor I have to give an FSD for any temperature. So I guess I'll either have to use a shunt resistor like Galileo, and just accept the way it changes sensitivity, or get one that's more nearly right.

Graham