Do infrared window comprimise the image quality, and if so, how does that effect your program?

The thing I am particularly concerned about is the limited angles and also reflections in an enclosed space such as an MCC bucket.

I have never used one an I would appreciate some feedback.

We just presented an extensive workshop on windows and viewports. Both radiometric measurement accuracy and detection can be severly affected by windows when the viewing angle is poor; essentially part of the frame can get in the way. Optimizing window placement and using good inspection techniques are both critical to success. Viewports are less susceptible mainly due to the super-wide angle lenses that are used with them.

Reflections can also be an issue (with both devices) because it is almost impossible to determine if a hotspot is a reflection or not by moving your position. Far better to deal with ELIMINATING reflective surfaces before you "button up" the enclosure during the process of installing the device. This will also make for much more accurate measurements.

We've learned a great deal from the mistakes the "pioneers" have made. Now we need to get the word out so others can reap the full benefits of these very useful devices.

John,

I agree with everything you say, I have been saying much the same for a long time now. My advice is always forget about temperature measurements through windows, yes it can be done but it is extremely difficult in the field and there are usually some pretty big assumptions to be made.

Do you have a paper on this? If so, can I have a copy?

bob@thermalvision.ie

If that is what you thought I said, then I'm sorry as that is not what I meant.

Two things:
1. temperatures CAN be measured accurately IF great care is taken in the design, installation and use of windows
2. without above, the problem is not only inaccurate and unrepeatable measurements, but also the probability that accurate DETECTION will be impaired.

I'm all for using these devices in places where we cannot otherwise safely inspect, but it is much more than just putting one in the middle of each enclosure.

I do not currently have a paper ready to share on this but hope too soon.

This message has been edited. Last edited by: John Snell,

John,

Fundamentally I agree with you, temperature can be measured through windows, but it is very difficult in the field and in a lot of cases too difficult for a level 1 thermographer. The biggest problem I find is generally there is no real reliable information on transmission rates when you arrive onsite (and there cannot really be) and as the windows are so expensive there is seldom a spare window to do some tests with. So, speaking in general terms it is easier to consider them a tool for the location of problems only.

I agree they can cause problems to be missed completely if incorrectly fitted, also in some cases, if you change viewing angle or have problems with vinneting they can cause you to think there is a thermal gradient, and this will lead you to believe there is problem when in fact there is not.

There is of course plenty of items that windows should be used on, but I have also seen them overused and fitted unnecessarily.

Finally I do believe that a lot of the problems associated with windows could be avoided if the people fitting them consulted a thermographer about their location and size. I personally do not get involved with the sale or fitting of windows anymore due to concerns over liability, but I certainly will point customers in the right direction and give advice.