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Adturb

G4+ and Thermocouple for EGT

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OK, so as per the title. 

I have a Defi EGT sensor and gauge, but as I've got a CAN display in the car I want to remove the gauge and put it through the ECU for display and logging purposes. Now I thought that it would be as simple as hooking it up to an AN Temp input, but after a bit more reading a thermocouple generates a voltage (55uV per degree C, as far as I can see for a k-type), rather than a resistance, like an IAT does.

Traditionally a thermocouple would be wired into an adaptor/ amplifier (I saw a PLX Devices adaptor mentioned in a post referring to ViPec 44) to give a linear 0-5V, with temperature compensation of sorts, output which can then be scaled on any AN V input, just like an external wideband. There is Raspberry Pi K-Type adaptor/ amplifier which is VERY cheap, I'm wondering if this would do the job?

However, the PC Link help file indicates to me that it can potentially take a thermocouple input directly? I know the Thunder can, as well as wideband, but I'm running a PNP EvoLink G4+. 

I'm a little bit frustrated as I though this would be as easy as pie, but the more I've read, the less straight forward it appears to be. On the upside it's quite interesting! :D 

 

IMG_7365.jpg

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The PNP link will not take a TC input directly.  I just googled the Raspberry Pi amp and most of them appear to be serial/SPI based so they will be no good to you either.  You need a 0-5V TC amp to feed into an analog input.  You can get these from many vendors, one low cost one that I know works ok is here: https://shop.vems.hu/catalog/amplifier-dsub9-p-129.html

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I've had a reply on another forum and someone is successfully using the Adafruit AD 8495 board, after a minor mod to rescale it for 0-1000 Deg C. As the output is a linear 0-5V I can't see why it wouldn't work? 

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If the output calibration is 0 to 5v being 0 to 1000 degrees C then it will work. If the signal does operate over the full 0.0v to 5.0v range then you may need to disable your fault values for the AN Votl channel used.

Scott

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Thanks for the replies, the board has arrived so I'll do the modification and see what the result is I can compare it to my Defi. Certainly been interesting as I didn't realise thermocouples generated a voltage, rather than a varied resistance as with an IAT, etc. Every day is a school day!!

Cheers 

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On 30.11.2016 at 9:18 AM, Adturb said:

I've had a reply on another forum and someone is successfully using the Adafruit AD 8495 board, after a minor mod to rescale it for 0-1000 Deg C. As the output is a linear 0-5V I can't see why it wouldn't work? 

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What minor mod is it u did, im getting 1.322 volt out of my amplifier in 14 degres C

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You need to add a voltage divider I use 2x 4.7k resistors and then run the board from the 12v supply - it take a bit if lineararity out but 1200C is approx 6v.

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