But you should consider before buying:
1. The module has no possibility of brightness regulation via change in the supply voltage. With series resistors / voltage dividers here is nothing to do. Also on the module itself is nothing more can be "screwed". It's just how it is!
2. The display is highly luminous, not to say highly luminous. This makes them easy to read, for example, under daylight conditions. The display - about the battery voltage in the night driving a car - can interfere but also because of the enormous brightness, even downright dazzling. Remedy is then only by stem a brightness filter. But who wants to be first found, most likely still for the red color, probably more difficult to achieve for green and blue. So clarify operating conditions in advance!
3. The measuring range of approximately 4 V (practically !, technically even less) to 30 V is gratifying far. The module draws on the holding itself according to its own measure only 6 mA, but this may be too much for some continuous operation situation may. Danger: At the two only 1 mm apart solder points for the two strands of the supply voltage = measuring is partly due to not only an appropriately for the pure purpose measuring weak dimensionable voltage but unsecured full voltage of each power source. Secondly, it needs a little picky and simultaneously high care requiring soldering, you want to the connecting lines (in exchange) extend and not risk that the power source is short-circuited, should be solved under harsh conditions even soldering or done the Lötzinnauftrag too abundant. Belaying Optionally with Leimtupfern!
4. In my measurement module the indicated duty machining deviated by 0.14 V from other voltmeters. Again, change can be it as far as I do not see anything - you have to live with it!
5. Whether or not a reverse polarity protection (protective diode) is built into the measuring module itself, could (and did) not test me. Here you would have - at a voltage source with potential polarity reversals - still provide a corresponding (external) protection!
