john banks

http://www.autospeed.com/A_0376/P_1/article.html

Comments? Was thinking of this for intake temp initially. RS supply the AD595 in packs of 25 for £290! But farnell.com do them for about £15 as singles. It amplifies the thermocouple output and compensates it so that you get 10mV/deg C which can be fed to a DVM, microcontroller or a display of your choice. Could also be used for EGT. The ready made meters are large and unfriendly.

The circuit is unbelievably easy. Cosie Convert advised me of a suitable K-type thermocouple which is about £6 from RS and can be fitted under the sleeve between the intercooler outlet and the throttle.

HarryBoy

Great idea! What is the RS Part number for the K type thermocouple John?

AndrewC

John,

A few people have done this in the past and had problems with the wires to the thermocouple being crushed once the j-clips were suitably tightened. I have tried this temporarily with a thermocouple straight into my multimeter (has a built in temp circuit) and it worked fine.

I seem to remember a well known North-of-the-border EVO convert had some thermocouples made up with stainless braided wires, may be worth considering.

Andrew...

john banks

Thanks Andrew -do you mean Sam?

AndrewC

Yes, I do mean Sam, I remember he posted about using s simple bare LCD temp display and probe, which prompted me to try my Multi-meter.

Andrew...

john banks

Wish search was on!

Sam Elassar

very subtle Andrew i like that.
i got my display unit from protherm as gavin suggested. not very expensive and it works aslo a trigger. so you can set it up to activat something at a certain temps. ( never used this faccility though.

i did crush the 1st probe, but this is because i moved it too much. i got a custom made aluminum one made from the same place. i will take a pic and post it later.

http://www.protherm.demon.co.uk/page29.html

john banks

Matt gave me the same link, but I couldn't see the neat little display you had installed on that page?

Sam Elassar

hi john
do you remember my unit? i remember asking you to check the temps while we were on track

it is the fist one off that page. it fits nicely in the ash tray i don't think you use it.

sam

john banks

Thanks Sam - it looked a lot neater and smaller in your car than on the page! Were you using a thermistor or a thermocouple then?

[Edited by john banks - 2/13/2002 5:54:12 PM]

Sam Elassar

i suppose it is just the same probe on the page encabsulated.

sam

john banks

Thanks Sam. I think I will go for the circuit as planned then using a thermocouple. It should be cheaper, smaller, and also much faster acting judging by Cosie Convert's display. Not that I am in his supporter's club or anything Thanks again. If you were just using a thermistor it could just be linked to a voltmeter. The thermocouple approach whilst a bit more faffy electronically seems to have many advantages over a thermistor. Or am I overcomplicating things (again?)

Sam Elassar

IT IS JUST A TEMPERATURE RPOBE? it is accurate, fast acting, cheap (30-40) and takes 15 min to fit. how complicated could it be!!!!!! you need to get out more man.

john banks

Its just that Matt said it was £60 (but I think he went for the 14721) and that it took 5 minutes before it gave a correct reading because it could not go in the airflow but was in contact with the metal? Did yours lag that much? Happy to pay that if it does a good job. The 14123 is said to come with a sensor but not on another page. I'll phone them...

BTW, I do get out rather a lot I just like to know what I am doing that is all! And I still don't get the whole picture. Please humour me thanks for all your help Sam! Sorry if I irritate you with my incessant questions.

[Edited by john banks - 2/13/2002 8:33:27 PM]

AndrewC

John,

Why not stick something like a Dallas DS18S20 (TO92 package) in the hose and use a µController to drive an LCD?

Andrew...


[Edited by AndrewC - 2/14/2002 12:36:41 PM]

john banks

http://pdfserv.maxim-ic.com/arpdf/DS18S20.pdf

Thanks Andrew. It looks a good device if I am going to link it to the uC.

mutant_matt

John,

Not quite - if there has been heat soak then it can take up to a maximum of 5 mins for that to go (depending on how you are driving and at what speed). When heat soak is not an issue (you've been on the move above 40mph), it's fast acting.....

Matt

john banks

So would the 14123 do with the (supplied?) sensor or does it need to be modified to avoid being crushed Matt? I'd just rather be reading the air temp rather than the metal temp...

[Edited by john banks - 2/15/2002 8:22:03 AM]

john banks

"Part No 363-0294 Exposed junction, fitted plug, 2m cable. [£5.76]

If you slacken the two jub clips around the rubber, then insert a
screwdriver from the I/C side, under the rubber and raise a slight tunnel
you will feel where the gap is between I/C and intake manifold.
Insert the t/couple so that the end is in this gap, then gently withdraw the
screwdriver and tighten it all back up.

EGT Thermocouple K type 397-1236 £14.55"

This is from Andy (Cosie Convert)



I think looking at the AD595 datasheet that it would be best operating off the full 12 to 15V power supply from the car without the regulator (the LM3914N didn't blow up why should this and it is only for a display so if it fries it fries) to get beyond 50 deg as would be required on a turbo car for intake temps and for EGTs.

[Edited by john banks - 2/12/2002 9:44:55 PM]