Review on PEMENOL DC-DC CNC USB Step Up/Down Power Supply Regulator Module: Adjustable Boost Buck Voltage Converter with Digital Display Voltmeter Ammeter and Battery Capacity Tester by Christopher Theriault

As some reviewers have noted, yes there is a lag when changing V output in PER mode. Be aware of this and it's not really a problem. I noticed that some small decimal places are missing (I couldn't get exactly 1.23V), but if you need that high accuracy, just use a precision lab power supply. The test you see in the video is an unloaded voltage. Applications can include direct LED powering or breadboard or even Arduino powering. If you are having trouble getting a link to a manual, you may need to email customer support who can provide you with a manual. Please note that the LEFT button must be pressed to increase the voltage and the RIGHT button to decrease the voltage. The temperature indicator is also only in C, as far as I know. In general, the device is excellent!