Not knowing much about the product means I may have been better not buying this. Did read online about 8 different uses. Used it to make sure it works..should have returned it but I balked at the $7 cost of return for the $17 I spent getting it..still should have returned it. It was ready to go with battery inside. Tested 9volt battery I think the ones that go in the smoke alarms. At first I thought it wasn't working but I think..only think I needed to apply to both ends. Product is fine..just not needed as found eventually that I had something that could test this battery...not sure it does the button batteries..which I don't have anything to test them..ie know whether they are viable or whether there is a problem with the device it is put in.