Review on 🚗 Zeltauto LED Digital Car Voltmeter: Reliable 12V/24V Vehicle Voltage Gauge Monitor for Auto Car Truck by Tutan Guliford

I bought two packs as a cheap voltage monitor for a 12v backup battery. As an EE, I tested them on my workbench with an input voltage of 6V to 15V. Both drew 40mA of operating current, which isn't very much, but it's not bad either. With an input voltage of 10-15 V, one device constantly showed a low value of 0.2-0.3 V, the other constantly 0.4-0.6 V. For example, if the actual voltage was 11 V, then one block showed 10.8 V on , the other 10.5 V. With an input voltage below 9 V, both displays fluctuated in a wide range (up to ±0.8 V!); This area held the right tension. So if you watch the fluctuating readings long enough, can you average something reasonable in your head? Doable, but not fun. The 0.5V offset error is serious for this application and can lead to an incorrect decision due to bad data. The good thing is that they are very cheap and come in packs of two, so you have a better chance of getting a usable version. They can be useful, but only if you (a) first determine the offset error using professional equipment, and (b) don't try to measure anything below 10V. For my purposes, I attached a reminder to my 0.2V offset block and am throwing away the 0.5V offset block.