OK I've opened it up. There are four '377' silver oxide batteries in the mounting shaft. I've included a picture of the commercial probe I mentioned that has a 20mm mount. The one I made is 1/2".
This has prompted me to order new batteries for the one I made !!!
Andrew
This has prompted me to order new batteries for the one I made !!!
Andrew
Andrew Mawson, proud to be a member of MetalworkingFun Forum since Oct 2013.