PicoScope 3000 Series User Guide
33
Copyright 2005 Pico Technology Limited. All rights reserved.
PS3000044 1.4
4.2
Powering the 3204/5/6
The PicoScope 3204/5/6 PC Oscilloscopes are normally powered from the USB port of
the computer. If the computer and the equipment under test (EUT) are both referenced
to the same ground, a "ground loop" may be created. This may degrade the DC accuracy
and noise performance when measuring small signals.
Typically, a ground loop is created when the PicoScope is connected to a mains-powered
computer and is used to measure a signal on another mains-powered device. In this case
the ground loop is created through mains earth, as illustrated below:
The majority of laptop power supplies (chargers) are floating and have no ground
reference. If, however, connecting your grounded laptop power supply causes
noise/offset problems, you can either use the oscilloscope with the laptop running on its
batteries or power the oscilloscope using the supplied mains adaptor.
If necessary, you should plug the mains adaptor into the socket on the back of the
oscilloscope (near the USB socket). It can be safely connected and disconnected during
operation without risk of damage to the oscilloscope.
