Desk-top oscilloscopes are very common in engineering labs. They are the first aid help devices when wave-forms need to be viewed and analyzed. Taking reads from an AC powered equipment with oscilloscopes may create a low impedance short between an o-scope AC ground and equipment that is being tested. The ground clip on a o-scope is actually tied to the ground. In order to avoid this problem differential probes can be used, but they are costly. Multimeter + has two differential inputs that have 10 M-Ohm input impedance. Both of these inputs can be used to view wave-forms up to 1 kHz (-3dB). High input impedance guarantees that there will be no shorts introduces when taking measurements from an AC powered equipment.

Isolated USB ensures that there will be no interference introduced by a PC power supply.

Typical application schematics:

The input and output signals are separated by an isolation barrier.

ISO7221.