Fluke 190 Series II User Manual page 92

Fluke 190 Series II
Users Manual
•
Additional safety. Since the commons are not directly
connected, the chance of causing short circuit when
measuring multiple signals is greatly reduced.
•
Additional safety. When measuring in systems with
multiple grounds, the ground currents induced are
kept to a minimum.
Because the references are not connected together inside
the test tool, each reference of the used inputs must be
connected to a reference voltage.
Independently floating isolated inputs are still coupled by
parasitic capacitance. This can occur between the input
references and the environment, and between the input
references mutually (see Figure 40). For this reason, you
should connect the references to a system ground or
another stable voltage. If the reference of an input is
connected to a high speed and / or high voltage signal,
you should be aware of parasitic capacitance. (See Figure
40 , Figure 42, Figure 43 and Figure 44.)
The input channels are electrically isolated from
the USB port and from the power adapter input.
84
Note
Figure 40. Parasitic capacitance between probes,
instrument and environment
Warning
To avoid electrical shock, always use the
insulation sleeve (Fig. 1 item e)) or the probe
tip when using the probe reference (ground)
lead. The voltage applied to the reference lead
is also present on the ground ring near the
probe tip, see Figure 41.
D
C
B
A