GERI Volt Amp Voltmeter Ammeter 2in1 LED Digital Voltage Current Measurement Meter DC 5V 12V 4.5-30V/100A with Shunt Red +Blue GERI&reg; Testing current: 0-100AMeasure range: DC4.5-30V Operating humidity1080%Operating temperature-10+65working air pressure80106kPa Display voltage and current simultaneously(the current is measured in the negative rail) Ground wire of testing end and power supply temninal is the same wire; quick refresh of about 500 ms 0.28" DC digital LED display in two colors (red+blue), bright LED, easy to read