Red Digital Voltmeter

Bought to test multiple points in a DC circuit simultaneously. You can calibrate each meter easily by tuning a tiny trimmer on its circuit board. All readings were consistent and within one hundredth of volt out of the package. Not bad for the price point. The readings were consistent across the 0-30 voltage range. Will read down to 0 volts with external power. Without one, the lowest reading is about 3 volts. Each meter consume around 20 milliamps but each meter was slight different. They are bright red and easy to read. Great if you are looking for reasonably accurate hobbyist grade ppanel meters.

Excellent 5 pack of digital meters that are large enought to easily read. Used for solar readings on batteries in kitchen so I dont have to go the battery and controller/inverter area to check the condition of the system.

These little meters are perfect for the small projects I always come up with requiring low voltage monitoring. The read out is surprising bright and clear and the option to have a separate lead to turn on the display when needed rather then being on all the time is very handy. The picture shown is supposed to be vertical and shows to AC power meters monitoring phase A and phase B of the 50 amp input to the RV and the DC meter this review is about below them is monitoring the DC voltage out of the convertor when plugged in or the battery voltage when not plugged in. The only minor problem I have with them is the mounting holes are very small and close to the circuit board making mounting the board a careful consideration so as not to short out anything. The price is right!

One of them came dead but the rest worked. Screen is bright. The two that I used in my project were displaying a very accurate voltage reading. I’m pretty happy with them.

Great little voltmeter! Mounting is easy, I 3D printed a shroud to help with this and added some smoky Lexan to cut the brightness down a bit and improve the contrast. Calibration is simple and accurate, I set the 10ths digit to roll over to the next value with the input voltage reaches 0.05V (i.e. an input voltage of 12.44 reads as 12.4 on the LED, and 12.45 reads as 12.5). The accuracy is very good over the input range and the 10ths digit does not jump around excessively. Overall this is a very easy to use and acceptable voltmeter for most projects. I used it here in a mobile amateur radio setup to measure power supply/battery voltage and boosted voltage. I do wish the 3 wires were accessible so you could join the white and red (voltage for the LCD driver and voltage to measure) but they solder to the surface of the PCB under the LED, not a big deal though.

I’m using this to monitor the state of charge of a LiFePo4 battery in my camper van, so I need accuracy between 12.9-13.4V. I calibrated the first unit to transition from 13.3 to 13.4 with a precision input crossing 13.35V. I’ll define a sub count as a change in the input of 0.01V. This mini DVM uses a micro with a 12 bit ADC, supporting a resolution below 0.01V, or 1 sub count (divide 30V range by 2^12). The voltage reference for the ADC comes from a cheap LDO regulator with +/-3% accuracy, which is why the calibration screw is needed. The specified variation of this LDO reference voltage suggests at most +\- 2 sub counts of accuracy loss between 50-100 degrees F ambient temperature, which is not bad. The long term drift of this reference is unspecified, and probably the most serious impact on accuracy over time. But again, a yearly recalibration should take care of that. I’ll check back in a year with an update. One last thing I’ll mention is the input (white wire) current. It is not quite zero. My measurement suggests there is a 125kohm resistor attenuator (probably 10:1) between the input and ground. So even if the unit is switched off (red wire opened) expect some current drain into input. For example, 0.1mA with a 12v input. Low enough for me to leave connected to my battery at all times, but about 10 times more current then a typical fluke DVM.

For two bucks a piece (with prime!), these things are great. I've only tried one so far, so I can't comment on quality. The only con for these is the calibration. There is a pot on the back that you can use to adjust calibration. But for instance if you calibrate it for 5v, it will be off at 12v and vice versa. So if you are using it to measure a wide range of voltages, the accuracy is not very good. These are better used to monitor a specific voltage for variations. Also, I don't know how good the calibration is over temperature. but again... two bucks each.... Pros: - low cost - fairly low current. at 13 volts, it draws between 10 & 20 ma. - good brightness Cons: - calibration screw is only for a limited range.

So cheap, and they work. Voltage accuracy is not great, but close enough for many applications.

Ça m'évite de sortir le voltmètre pour vérifié l'état des batteries. Un calibrage, par contre est nécessaire pour chaque voltmètre. J'aime bien.

remarkably accurate compared to my fluke. using to monitor 12 batteries in rv.

A lot of buzz introduced into the power line. Use a bypass capacitor.