Hi All. I bought this little AC Voltage Meter, when they first came out some time ago. I have left it plugged in our 5er for years now. I have seen on the RV Forum, that a lot of RV'ers thinks this AC Voltage Meter is not very good. Well, to set you all straight, this little AC Voltage Meter, is really a great little meter to have in your RV, to watch the incoming Voltage. It is dead right on target, and to make sure it is, check it against your Multimeter as I did. If by chance, your off by a bit. Take your pocket knife, and give the upper corrner of the AC Voltage Meter a little bit of a twist, and the clear plastic cover will come off very easily. Then just test your out-let with your Multimeter, and adjust the AC Voltage Meter at the bottom of the AC Voltage Meter, as there is a small lever, that you can adjust your Voltage Meter, to the + or the - to exactly to read what your Multimeter shows. Why waste money on an AC Voltage Meter that costs a lot more. This one does a perfect job of letting you know exactly what your incoming Voltage is. Good Luck. Happy Camping. Dan & Jill