LeCroy AP034, Instruction Manual

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AP034-OM-E Rev D ISSUED: January 2000
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displayed above the graticule for a few seconds
after a change is made by turning the knob (refer
to Figure 3). In prior software versions, the
channel O
FFSET
knob adjusted the offset of the
oscilloscope input rather than the probe offset.
When the AP034 Active Differential Probe is
used with LeCroy oscilloscopes with older
software versions, it is important that the channel
offset (controlled by the channel O
FFSET
knob)
remain set to 0.0000 V. Moving the displayed
waveform with the channel offset rather than
probe offset will not re-center the dynamic
operating range of the probe. Offsetting the trace
with the oscilloscope channel offset introduces
the possibility of erroneous waveforms that result
from overloading the probe.
AUTOBALANCE
The AP034 Active Differential Probe incorporates an
Autobalance function to remove the DC offset from the output.
Autobalance must be invoked by you. When power is first
applied, the probe will return to the internal values resulting from
the last Autobalance cycle. For Autobalance to function properly,
all signals must be removed from the input.
After several minutes of warmup, or when the probe is exposed
to a large shift in ambient temperature, some DC offset drift may
occur from thermal effects in the amplifier circuitry. To initiate an
Autobalance cycle, remove the probe from the test circuit and
select the AUTOBALANCE menu selection in the oscilloscope
“COUPLING” menu for the channel the probe is connected to. If
the probe is being used with the ADPPS power supply, remove
the input signal, then push and hold both O
FFSET
buttons for two
seconds. The AP034 must be terminated into 50
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Autobalance.
Upon successful completion of the Autobalance cycle, all three of
the EFFECTIVE GAIN indicators will be briefly illuminated. If an
input signal is present during auto balance and the routine fails,
the EFFECTIVE GAIN indicators will not illuminate. The probe
will then revert to the offset values resulting from the last