Teledyne LeCroy WaveLink Differential Probe Series (13-25 GHz) - Manual (Page 33)

Operator's Manual
WL-HBW-A-OM-E Rev B 27
new socket can be soldered onto the tip.See Replacing Spring-Loaded Tips and Tip Sockets on the
Positioner Tip (on page 1) for instructions on replacing tips and sockets.
Probe Grounding
In most cases, when the common mode portion of the signal consists mainly of lower frequencies,
the probe does not need to be connected to the ground of the circuit under test. This minimizes the
effects of ground loop currents. Any signal corruption caused by not having the probe connected to
ground of the signal under test is common to both inputs and is rejected by the differential
operation of the probe.
However, in an environment with high RF ambient noise, it may be better to connect the probe
ground lead to a good RF ground near the point where the signal is being measured. Find out if a
ground lead is necessary by making a measurement with and without a ground lead. Use the one
that provides the least signal corruption.
Capacitive coupling from AC mains may cause truly floating devices (like battery operated devices)
to exceed the common mode range. In such cases it is recommended to connect the probe ground
to the device under test.

Circuits powered from laboratory bench power supplies normally have floating
outputs.

Floating circuitry may exceed the common mode input voltage, causing damage to
the probe. Always use a ground lead when testing floating circuits.
Positioning of the Input Leads
Normally the performance of the Solder In Lead and Positioner Tip Browser is not affected by the
position of the amplifier module. They can be mounted straight upright or on an angle. However,
when it is necessary to mount the module parallel to the board, the maximum performance is
obtained when the + sign (printed near the positive input on both the SI Lead and the PT Tip) is
upward facing.
NOTE: The flexible cable connecting the input tip to the amplifier module is reasonably insensitive to
placement, but can be affected by large signal emitters on the device under test, so avoid placing it
near these types of signals