Many windows have nowadays Low-E, low-emissivity, coats to enhance its energy efficiency functions. That is why it is relevant to ask can Sparklike Handheld measure Low-E coated IG units.
The answer is yes, if the other side of the double-glazed glass is clear glass. That is only when you can measure through it.
What about other coatings and laminations?
Also, the limitation of spark technology is that it can measure double-glazed units with just one low-e coating. With Sparklike Laser you are able to measure double and triple glazed insulating glass units with coatings and lamination.