Fluke 1503 insulation tester fluke fluke 1503 the fluke 1503 insulation tester is compact rugged reliable and easy to use with its multiple test voltages it is ideal for many troubleshooting commissioning and ideal for preventative maintenance applications additional features like the remote probe on this tool save both time and money when performing tests the 1503 is ideal for all your basic electrical insulation testing and handles the most common tests at a most affordable price