Review on 🔋 bayite Pack of 5 Three-Wire Calibratable DC 0~30V Red Digital Mini Voltmeter Gauge Tester: Reliable Car/Motorcycle Battery Monitor & Voltage Meter with 0.36" Red LED Display Panel by Rodney Mendoza

At two dollars a piece (with an extra charge!), these things are great. I've only tried one so far, so I can't comment on the quality. The only negative for them is the calibration. There is a potentiometer on the back that can be used to adjust the calibration. However, if you calibrate it to say 5V, it will disable at 12V and vice versa. So if you use it to measure a wide range of voltage, the accuracy is not very good. They are best used to monitor a specific voltage for changes. Also, I don't know how good the temperature calibration is. but then again. two dollars each. Advantages: - low cost - fairly low power. at 13 volts it draws 10 to 20 mA. - Good brightness. Disadvantages: - Calibration screw only for limited range.