The Bartol Magprobe Solenoid Valve and Relay Tester's Operation is Completely Isolated from Computer Loading Issues often Present with a Voltmeter Test Instrument. Before the Advent of The Bartol MagProbe the Cost of Service in terms of Time, Manpower and Lost Productivity and Lost Potential Revenue was Significant. Checking Electrically Operated Solenoid Valves and Relays using a Conventional Voltmeter Requires Shutting Down the Production Line in Order to Isolate the Defective Part and/or Shutoff Computerized Controls to Prevent Loading of the Computer Output Drivers.