I ended up getting 5 of these, two for me and one each for my sons. Received an extra due to a misunderstanding when ordering. Just as. On one of them, if a 9V DC battery was below 8 volts, it would read the household AC power as high, if it was 120, for example, it would read 180. On a dryer between two legs with 120VAC it would read 360VAC. With a new battery, the voltage was displayed correctly. Another doesn't matter, if the battery was new 9vdc, at 5vdc it would read a fully charged car battery. Shows 120 VDC as 73 VDC. They're cheap, about $10. Buy 6 or 7, 3 or 4 should work properly. Just like buying thermometers in the store, look for 5 out of 10 that read 77F and don't buy the one that says 70, 90, or 74.