rockjeep73

Had some ideas floating around in my head, and I was trying to figure out if there would be some way to use an EGT probe to switch something on and off based on a set temperature, which could be adjusted with a potentiometer or something of the sort? I guess it would help if I knew how an EGT probe operated, what do the two wires from the probe do?

Cory

DR3500

The probe creates voltage that the gauge converts to a temperature reading.

rockjeep73

that doesnt help me much, im looking for a way to turn this voltage into an adjustable switch to toggle an accessory. and there are two wires on a probe, voltage in? voltage out? or???

Dr. Evil

In laymans terms, the EGT probe is a K type thermocouple. It is made by twisting two different type of wire together. The end that goes into the manifold sends milliVolt signals to the cab mounted guage (which changes with the changes in manifold temperatures).

We are talking about very small voltages (for example, at 1000 deg C a K type thermocouple puts out 41.276 mV). If you do anything to change the mV signal between the probe and the guage - the reading at the guage will be very inaccurate.

Back to the drawing board.....

rockjeep73

first off, what im talking about has nothing to do with a gauge, just the thermocouple. but youre saying that the voltage changes in the thermocouple are so small that you couldnt do anything with them? I know that with SPA gauges and maybe some others, you can attach an accessory that can be triggered on and off based on a preset temperature, this is what I would like to do, but without the having to utilize the gauge, if possible.

Smkndzl

yea , millivolts created by the thermocouple , maybe something like a oven temp control switch is what you need , but in a DC format.

rockwithjason

what you want is possible but it would require some electronics to support the operation. You could use an amplifier to boost the signal to a usable level and then set up a comparator to do the switching. You would have to look up the design data for the components and then match them. You could have the comparator drive a relay to do high current switching.

Dr. Evil

OK, I understand what you are saying now.

Yes, the voltage from the temperature change at the probe is very small - so you would have to amplify it as previously mentioned.

rockjeep73

hmm...im no electrical genius so a lot of this is foreign to me, looks like I will have to start doing some research.

an amplifier and comparator you say?

rockwithjason

yeah...the electronics can get involved. You could use a simple transistor to up the signal levels. A comparator compares two inputs and gives an output based on directions you set up for it.