... is the best on-site surface magnetic field measuring instrument. Application:Measurement of surface magnetic field, ... DC electromagnet.Features:1. Onekey zero adjustment automatically2. Measuring range change automatically3. Lock the change of peak ... . Polarity identifyingTechnical Parameters: Power Supply6V batteryMeasuring Range0-±30.0mT,0-±300mT,0-±3000mTthree gears,gear shifting ...