Surface Thermocouples Mount

No.

Use a mechanical fastener and thermally conductive grease.

As Lyn notes, mechanical attachment (e.g., spring clip) is strongest. Thermal grease/mastic/compound can come in different consistencies, some of which may also serve as adhesives in case mechanical fasteners are awkward. See the application notes for whichever type you plan to use.

Hi all,

thank you for your suggestions.

In fact, i already thought of using mechanical fasteners, but we want to find a solution without modify the vehicle parts. i found this adhesive. it's a little bit expensive:

http://media.digikey.com/pdf/Data%20Sheets/MG%20Chemicals%20PDFs/RTV167.pdf

I'm not sure that it will withstand hight temperature and vibrations.

I'm still looking for other solutions.

Thank you for you interest and for your help

With respect

Hi, we use Loctite 615 Epoxi-Patch adhesive to adhere thermocouples to hot surfaces with little vibration.

For ambient temperature we sometimes use regular epoxy glue (the two parts commercial thing you can by at any store)

For some motors we solder the thermocouples directly in the motor surface.

I am not sure if any of these will be OK for your application.

In any case is really important that you use the minimum amount of glue/solder you can.

I hope this information will be useful for you

This is my last pronouncement on the subject.

Silicones have a relatively high coefficient of thermal expansion so the bond line will grow when heated meaning that the TC will move farther away from the heat source, so, if it doesn't fall off completly, the reading will be slightly off. The thermal conductivity is probably not as good as some adhesives specifically made for TC attachment.

None of this will probably matter to you.

Good luck.

Hi all,

thank you for your help and your clarifications.

It's clear that the best solution was to weld them directly on the surface or to use mechanical attachments. Theses solutions were rejected by the project manager who don't like to modify the engine surface and we will try for instance adhesives.

I've already found theses three solutions and we will choose one of them :

http://www.omega.com/Temperature/pdf/CC_CEMENT.pdf

http://www.omega.com/Temperature/pdf/OT-201.pdf

http://media.digikey.com/pdf/Data%20Sheets/MG%20Chemicals%20PDFs/RTV167.pdf

For the first two products, it is mentioned that they are used for surface measurement probes. But, it can be a marketing information because they sell also probes!

Thanks

with respect

Omega is a trusted vendor, they have a lot of technical information available. They sell a lot of things, as they offer complete solutions.

You can do a search on technical specs to measure temperature on hot and vibrating surfaces.

Good luck

I would omit the advice of the project manager and discuss this;

Welding the two wires separately to the surface does not really change it.

Adding fastners and glue has a huge inpact on the emissivity and thus the ultimate temperature of the measured surface, certainly in the domain you are going to work.

The discharge welding used in this domain simply creates a small spot weld.

The thermocouple is realised by the double junction with the surface metal and measures the real temperature in that region, you don't risk that the two wires accidentally cross due the vibrations and the temperature is measured some mm from the surface.

Wow! 572 fahrenheit! You must be trying to read exhaust temperature.

You will be reading surface temp. unless you install a thermocouple well or bung.

The easiest way to install a surface temp reading T/C would to be clamping the tip to the exhaust pipe with a hose clamp. Make sure you route your wiring clear of anything that will abrade it or you will be taking the temperature of where the T/C wire shorted together!

Best of luck

BOBCO

stainless steel cable ties, stainless steel wire etc or even regular wire, all of these can be used to fix the Tc in place.

Remember K-I-S-S.

Sensors need good surface mating with a specified pressure for accuracy.

I can't say how it can be attained by adhesives only.

You might want to use thermistors instead. You could put them in a bolt hole with some heat conductive grease. Of coarse the wires would have to be bolted down close to the sensor. This would avoid disturbing the engine with glue or welding.