The Model 428B Clip-On Milliammeter measures the magnetic field, which exists around the wire carrying dc current. Operating the instrument Is simple. After zero setting, the two jaws of the probe are clamped around wire (arrow on probe head indicates direction of conventional current flow) and the meter will indicate the current. There are nine current ranges starting from 1 ma to 10 amp full scale deflection. The sensitivity can be increased even further by looping the wire several times through the opening in the probe. The current indication is virtually insensitive to super* imposed ac signals and the series loading of the circuit is less than 0.5 µh. A large amount of feedback provides great stability. With the Mode] 428B currents can be measured as easily as measuring voltages with a voltmeter.