Damp Meter Recommendations

Do the damp meters with pins cause any lasting damage to the Motorhome interior? I have read on various forums that they leave lots of small holes and what are the alternatives?
Any recommendations would be appreciated re accuracy and cost.

I  used a pin type for checking our Nuevo when we had it and you can't see the pin holes they make. The alternative are the protimeters the professional uses, costing £150-£200.
Go on eBay and search 'non-invasive damp meter' and you will find some from China for under £30 but no idea if any good.