Four models are available for general purpose testing which include a low-voltage model. All are portable, self-contained instruments designed to give rapid and accurate measurements. Four of the models feature an analog display having four selectable test voltages of 100, 250, 500 and 1000 V dc, measuring insulation resistance up to 2000 M-Ohms, and an ohm range to 5000 ohms. The other model has four test voltages of 50, 100, 250 and 500 V dc measuring insulation resistance up to 1000 M-Ohms.