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#1 2010-02-07 15:29:30

thejd
New member

Measure Resistance

Hi,

Im using an Analogue Vehicle Temp sender, which is a resistor I believe. The Vehicle ECU uses 5v for sensors etc.

The ADC anaolgue Pin measures Volts.

What do I do? Can I convert Ohms into Volts?

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#2 2010-02-08 22:55:26

AlanH
Member

Re: Measure Resistance

does the sensor have 3 contact points?  +5v Gnd and output.  just hook the 5v and ground to the gnd and 5v pins and then use one of the pins 1-8 you will get a reading between 0 and 255.  Using a seperate pyrometer you should be able to determine the ratio to convert the analog signal.

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#3 2010-02-09 09:59:04

thejd
New member

Re: Measure Resistance

Hi Alan, thankyou for replying.

The Anaolgue Vehicle Temp sender is 2 wires.
1 wire goes to the Common GND for all the vehicle sensors, the other wire goes to the ECU Temp Input Pin.

Its a resistor, I tested using a multimeter and the resistance rises and falls with heat applied/removed.

I tried putting the Temp Sensor in 'Series' (its a resistor me thinks) with a regulated 5v PSU, but it just reads 255 regardless of Temperature applied to the sensor.

Cheers JD

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#4 2010-02-11 23:28:09

thejd
New member

Re: Measure Resistance

The answer!! It works

To measure a resistance, you must transform the variations of your resistance into voltage variations.
This is done using a voltage divider, where one of the resistors is fixed and of a know value, the other is the one you want to measure.
Wikipedia has a nice page on the subject:
http://en.wikipedia.org/wiki/Voltage_divider
Using the equations, you measure voltage, and deduce the value of your unknown resistor.

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