Fluke 1503 Insulation Resistance MeterFluke 1503 Insulation Resistance Meter The Fluke 1503 is a great choice for basic residential and commercial electrical insulation testing. This rugged, compact tool fits in the palm of your hand. The 1503 is the same form factor as the Fluke 1507 but with a few less features. You can count on it to handle the most common tests at a most affordable price. Additional features, like the remote probe, reduce the time needed to perform repetitive testing.