Infrared Camera - Penetrable Material

[martinb]

Hello

This is my 1st post, so not sure if I have the right forum.
I am conducting an experiment in a Perspex wind tunnel and I need to measure the temperature of a plate inside the wind tunnel. thermocouples are not an option. I have to use an ir camera. I'm using a Flir i7 camera. I need to cut out a section and replace it with an ir penetrable material. I have heard that cd cases work, but any I have tried have failed.
Any suggestions?

Thanks

[mikeselectricstuff]

Zinc selenide
Gallium Arsenide
Silicon
Germanium
Maybe thin polythene
Sodium chloride

All are likely to affect the temperature calibration though. Probably easier to mount an IR temp sensor inside  the tunnel or in a small hole

[LukeW]

In addition to the materials mentioned by Mike, you've also got the thallium halide materials like KRS-5 and KRS-6. They're even more transmissive down into the far infrared than ZnSe, but they're toxic and pretty exotic materials. ZnSe, Si and Ge are probably the most common window materials in basic thermal IR applications.

[Fraser]

FLIR disposable lens protectors for thermal cameras use the 12 or 25 micron shrink wrap plastic called Polyolefin, that is commonly found as the WRAPPER on CD cases.

I bought a large roll of the plastic very cheaply. IIRC around GBP5 for 1mx20m. It is pretty strong so should survive in a wind tunnel ?

Additional info added:

I purchased 25 micron Polyolefin from the following company and it works very well. I just tried a piece in front of my E4 and the camera sees through it fine.

Bee Beautiful .....www.beebeautiful.org.uk

http://www.ebay.co.uk/itm/20mtrs-Polyolefin-Shrink-Wrap-Film-25-micron-450mm-/350800488552?pt=UK_Packaging_Materials&hash=item51ad56a868#ht_1387wt_1018

[SeanB]

Nice to know, I use that at work for shrinkwrapping, so have rolls of it.

[Fraser]

http://www.kube.ch/plastics/

[mikeselectricstuff]

What sort of plastic is it they tend to use on a standard PIR sensor people tend to use at home for things like outside light on/off etc?

The plastic around the sensor area normally looks white to the eye but is obviously transparent to thermal IR frequencies, and often acts as a segmented lens for the PIR sensor itself.

Polythene/polyethylene

[olsenn]

Everything penetrates Paris Hilton

[Fraser]

There are many plastics that are transparent to a greater or lesser extent at thermal wavelengths. Even black bin bags are transparent ! A key issue is material thickness. The thinner the better when it comes to transmission losses in plastics.

Experimentation is recommended