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[Kiwidazza]

Heeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeelp

ok don't know whether this is the right place or not however this question relates to an automotive application. What I have is a voltage from an Engine Coolant Temperature sensor (ECT). As the temperature increases the voltage sent from the ECT to the ECU decreases. I would like to run a temperature gauge off this wire going to the ECU but I can't because it changes the signal and basically causes the engine to run rough as guts. What I would like to do is take this wire and use it as an input into a little circuit that gets its own power supply. I would then like to subtract the sensor voltage from a reference voltage (5V) and use this as the output to the temp gauge.

Is there an easy way to do this? I can get the required parts and assemble but have absolutely no idea what I'm doing with this side of things.

Is anyone able to help?

 

[Super_voip]

Sounds like an inverting op-amp is all that is required, if you keep the amplification at x1 then there will be a very high impedence and the ECU won't know it's there. So google, opamp inverting circuit, and look for the easiest one.

 

[Kiwidazza]

Cheers mate. Help from good old Brissie eh. Wish I has the weather in Palmy.

 

[audioguru]

Sounds like an inverting op-amp is all that is required, if you keep the amplification at x1 then there will be a very high impedence and the ECU won't know it's there. So google, opamp inverting circuit, and look for the easiest one.

An inverting opamp needs two resistors.
Its input impedance is the resistance of its input resistor.

If the opamp circuit is non-inverting follower then maybe no resistor is needed and the input impedance is extremely high.

 

[Kiwidazza]

Foul language deleted, and 48 hour ban.

Moderator.

 

[Hero999]

Please post the schematic.

Did you use a non-inverting amplifier on the input to give a high impedance input?

If you're getting grief from someone via PMs then please reply to them via PM rather than telling everyone on the forum about it as nobody here cares.