LeCroy DA1855A Operation page 10

DA1855A Differential Amplifier
Power up indication
Precision Voltage Generator Offset Voltage
3-10
usage, the instrument may be left plugged in at all times and the
power switch left in the 1 (ON) position.
Upon turn-on, the model number and firmware version are briefly
displayed in the PVG readout. For example, 1855.12 indicates
that the instrument is a model DA1855A and the firmware version
is 1.2.
The rear panel OFFSET VOLTAGE BNC (PVG) output
connector, is a monitor of the Precision Voltage Generator (PVG).
The voltage present on this connector is the same voltage as that
applied to the –INPUT when the –INPUT coupling is set to V
or internally to the DA1855A when V
OFFSET VOLTAGE output can be used to monitor the PVG with
a digital Voltmeter (DVM). A low pass filter between the PVG
output and the –INPUT removes radio frequency interference
(RFI) from the signal. This filter does not attenuate the PVG
signal.
The PVG output is not attenuated by the input attenuator or
probes, whereas the input signal is. Therefore the effective range
of V is increased by a factor of 10 when the 10
COMP
ATTENUATOR is selected or a 10 attenuating probe is used to
attenuate the input signal. The PVG numerical display reflects the
attenuator setting and probe attenuation when the probe is
readout encoded. As an example, if there are no probes
attached, the 10 ATTENUATOR is selected and the display is
set to read –155.000, the PVG output will actually be –15.5 Volt.
The decimal in the display will be in the correct location to
indicate the voltage at the PVG output when no probes are
attached and 1 ATTENUATOR and X1 GAIN are selected.
The OFFSET VOLTAGE BNC (PVG) output also presents the
same voltage used internally for differential offset when V
selected. Because the PVG is applied to the amplifier to create a
true differential offset, the relationship between V
voltage at the OFFSET VOLTAGE BNC (PVG) output (changes
with the amplifier gain selection according to the following table:
The maximum V is multiplied by any probe attenuation
DIFF
factor.The DA1855A front panel displays the correct offset
referred to the instrument input.
ISSUED: July 2002
is selected. The
DIFF
DIFF
and the
DIFF
DA1855A-OM-E Rev A
COMP
is