Transparent window in shielded box

[CatalinaWOW]

You can't really answer your question without numbers.  Any display not intended for stadium use is quite small with respect to the wavelength of the power mains.  There will be quite a few dB of attenuation just from the aperture.  A screen with a low resistivity layer will provide even more attenuation, but only you can say what good enough is.  Do you need 40 dB, 80 dB or 120 dB of attenuation?

It is both easy and hard to find how much you need.  Just operate your device without an enclosure in the environment that is pertinent and measure the noise.  The hard part is making sure that the noise you observed is field induced since there are many sneaky conductive paths which can affect this. 

The pinhole camera idea, or a small film camera if your box is big enough can answer the other end of the question.  With the pinhole, or no window at all what is your observed noise.  The two measurements will tell you what the window attenuation has to be until you work on other noise sources.

[pickle9000]

Use an ultrasonic transducer and pickup outside the box.

[slugrustle]

because gluing on a piece of glass to a chassis element is like dodgy. If you put a gasket it gets a bit of impact resistance since its compliant. I don't recommend doing that. Even picture frame don't glue glass.

A home window is glued with stretchy silicone too. The electronics glue is hard.

Thats my opinion anyway.

Like bonded glass is usually bonded on the whole surface with transparent adhesive, or its reinforced (be it like cell phone glass 'corning' or car windshield which is multilayer)

Pretty sure your ITO glass is fragile normal glass.

I would love to hear from a glass expert. Its just based on my observations on how I see glass implemented.

Thanks for explaining.

Agreed that ITO glass is just normal glass with a thin layer of ITO on one side.

Another issue with gluing is the difference in coefficient of thermal expansion between the enclosure and the glass.

[slugrustle]

Use an ultrasonic transducer and pickup outside the box.

Vibration would be bad in this application, but along similar lines, a plastic fiber optic cable might be really nice.  The TOSLINK ones aren't insanely expensive.

[radar_macgyver]

Seems like you can order an ITO-coated PET sheet from Adafruit: https://www.adafruit.com/product/1309

They also carry a smaller ITO-coated glass sheet. The PET sheet will likely scratch very easily, but would lend itself to gluing with conductive epoxy.

For what it's worth, Keysight uses an ITO sheet over the LCDs of various spectrum and network analyzers, presumably to meet radiated emissions specs. The usual method uses a fabric-over-foam gasket to couple the ITO-coated sheet to the chassis. One of Shariar's videos may have shown this in detail, though I can't remember which one.

[pickle9000]

Use an ultrasonic transducer and pickup outside the box.

Vibration would be bad in this application, but along similar lines, a plastic fiber optic cable might be really nice.  The TOSLINK ones aren't insanely expensive.

If your only doing one data point any led an optical fiber and use a handheld RPM meter.