Teledyne LeCroy DA1855A - Manual (Page 21)

Operator’s Manual
922258-00 Rev A 15
PVG to null out an input voltage up to ± 155.00 Volt which is ten times larger than the actual PVG
voltage.
The increase in common mode voltage range also applies when using attenuating probes.
When the DA1855A is used with attenuating probes that feature readout, the PVG display is
changed to indicate the voltage at the +INPUT probe tip which will bring the amplifier output to
zero.
When connected to a Teledyne LeCroy oscilloscope via the ProBus interface, the oscilloscope
OFFSET control increments or decrements the PVG’s output voltage and the offset value will be
shown on the six PVG front panel indicators. The new offset value will also be displayed on the
oscilloscope’s screen for a few seconds after a change has been made.
When connected to an oscilloscope not provided with a ProBus interface, the PVG can be accessed
by means of push buttons. Above each digit is a push button which increments the corresponding
digit by one when pushed. When held, the digit continues to increment, eventually incrementing the
next higher digit.
Similarly, below each digit is a push button which decrements the corresponding digit.
The ± button above the left-most digit changes the PVG output polarity. The ZERO button below the
left-most digit sets the output to zero and invokes the PVG's Auto Zero function. PVG absolute
mode: DA1855 PVG increment and decrement buttons always function to increment or decrement
the voltage display respectively. When decrementing from a positive voltage, the display always
stops at zero. To obtain negative voltages, the ±± button must be pushed, and the increment button
is used to increase the magnitude of the negative voltage. This operation is natural if simply setting
a voltage, but unnatural if moving a displayed oscilloscope waveform. This is known as the PVG
absolute mode, and the only mode available in the original DA1855, (non “A” model). The DA1855A
retains the option of operating in this same manner as well as supporting PVG roll through zero
mode.
NOTE: When the DA1855A is controlled remotely through a Teledyne LeCroy oscilloscope, neither
PVG absolute or PVG roll through zero modes apply. When operated remotely, the PVG value is
controlled with the use of the OFFSET knob on the oscilloscope, when in effect, operates in the roll
through mode.
PVG roll through zero mode: The DA1855A increment buttons are oscilloscope waveform related by
factory default. The increment buttons move a displayed oscilloscope waveform upward and the
decrement buttons move the waveform downward independent of the PVG polarity. Decrements
from a positive voltage will roll smoothly through zero. This is known as roll through zero mode.
Toggle PVG modes: To change from roll through zero to absolute mode of operation hold the PVG
ZERO button and press the ± button. Change back to the roll through zero mode by repeating the
same operation.