This review is designed to help you figure out how to use the curve tester that did not come with any instruction or power supply. Note that when calibrating the tester set the scope to 1V per graticule. Sorry I forgot to mention that. This device will not work at 11V and it barely works at 12V. It will work at any voltage above that and up to 24V. However, the output voltage will rise with the input voltage and that makes the calibration different. It should have had a voltage regulator on board to prevent that. Other than that, it seems to work OK. No overheated parts or any other adverse effects that I can find.