Calibrating Temp Gauge To Sensor With Resistors?

[Dan_J]

bit stumped so figured i'd post a thread

i've got a gauge that doesn't match up to a sensor/s, its over reading, i've wired resistors in series( if i wire in parallel temps go higher which is not what i need) on the sensor wire which does change the temp down as its over reading.

my problem is that when temps go hot to cold the temp display is kind of stuck and will only change with in 10-20 degree or so when in reality it should be reading much higher even though that cold base temps are spot on.

do i need some other components wired in other than resistors?

any clues ?

thanks

[r31slpr]

( if i wire in parallel temps go higher which is not what i need)

That's because wiring resistors in parallel reduces resistance.

How did you figure out which resistors to use so far?

I'm assuming single wire sensor?

Only thing i can think if at the moment is hook up a pot and some power to the gauge and see what resistance gets you from min to max.

What sensor are you using at the moment? If its pretty close find the data sheet and find the resistance curve, that should give you an idea of which pot to use.

Once you figure out an appropriate resistance range, you should be able to find another sensor with the right curve.

What gauge is it? Any chance you can get another sensor from the manufacturer?

[Dan_J]

am using a 'resistor wheel' from jay car which is just a knob on a dial that alternates to different resistance, also have hard wired resistors in to see if there was a difference .

using a 2 pin sensor although resistors are only connected to one wire obviously

the gauge is way off as the sensor that it came with is only a probe, not an actual bolt in water sensor so matching up a sensor to work with no changes to the circuit wont do it.

have tired a few sensors from ecu coolant to normal 2 pin aftermarket sensor and the temps are still getting stuck within a band

my wiring is pretty simple :

sensor + -> resistor in series -> wire to gauge

is this one for the guru's or cant it be done?

Edited June 29, 2013 by Dan_J

[Chris Rogers]

Thing to bear in mind thought is that the sensor is a thermistor and the output of it IS NOT linear. Google thermistor and you should get an understanding on how it works.

Adding resistors won't fix it , the correct sensor for the gauge will.

[Dan_J]

so adding other components to calibrate it cant be done?

shall bin it then..

[r31slpr]

the gauge is way off as the sensor that it came with is only a probe, not an actual bolt in water sensor so matching up a sensor to work with no changes to the circuit wont do it.

So you have the sensor that it came with?

What brand gauge is it?

Thing to bear in mind thought is that the sensor is a thermistor and the output of it IS NOT linear. Google thermistor and you should get an understanding on how it works.

Depends on the application, i was under the impression that most auto water temp sensors were rtd's, which in that case should ideally be linear. I may be wrong though.

Dan_J say's it came with a probe which could be either.

so adding other components to calibrate it cant be done?

shall bin it then..

Not worth binning it yet, shouldn't be too hard to find the right sensor