Features: Through-hole design: No wiring difficulty. Measure positive or negative current. No current direction limitation Electrically isolated from high voltage power source which eliminates risk to delicate monitoring equipment and also minimizes safety concerns Display Voltage or (+ -)Current. Voltage Range: 5V-120V. Current range: 0-100A Large wire capability: Diameter of the hole through sensor is 3/4 inch(19 mm) Loop through sensor multiple times to strengthen signal. For example, if your current signal is only 0.2 Amps, you could loop the wire through the sensor 10 times and the signal would by 10X for stronger and would appear as 2.0 Amps Description: Hall effect current meter reads current by detecting the magnetic field around the wire, there is no electrical contact which eliminate risk to delicate monitoring equipment and also minimizes safety concerns. The sensor doesn'for t get hot like the current shunt sense resistor which can have thermal temperature heat dissipation issues. Three display modes: 1. alternately display Amps and Voltage 2. only display Amps 3. only display Voltage Specifications: Measurement Range: + -100A Accuracy: + - 1% Resolution: 0.3A Working current: 7-15mA Power supply: for DC 5-120V Product Dimensions: 48mm*29mm*23mm Mounting hole: 45.5mm*25.5mm Sensor hole diameter: 19mm Operating temperature: -4F - 140F (-20C - 60C) As the resolution is 0.3A, the current reading might be flickering with 0.3A difference. For example, if the current is 1.7A, you might see a 1.7A and 2.0A alternatively. This is normal. If your signal is too weak or you are not getting the resolution you want, you can coil the wire through the current sensor as many times as you want to double, triple, or quadruple the sensitivity or resolution. For example, if your current signal is only 0.2 Amps, you could loop the wire through the sensor 10 times and the signal would by 10X for stronger and would appear as 2.0 Amps. Note:We have more detailed manual, if you need an electronic user manual, please contact us. Package included: 1x Digital Voltmete Ammeter 1x Hall Effect Sensor