Teledyne LeCroy DA1855A - Manual (Page 39)

Operator’s Manual
922258-00 Rev A 33
• By using the DA1855A in the comparison voltage mode and the oscilloscope in a high
sensitivity setting, highly accurate voltage measurements can be made.
• The Precision Voltage Generator can be used as a position control which allows the
DA1855A to operate in its linear region.
Differential Offset Operation (V
DIFF
)
Leave the DA1855A set up as in the previous exercise or set it up as follows:
+INPUT DC
–INPUT V
COMP
BW LIMIT FULL
GAIN X10
ATTENUATOR ч ч1
INPUT RESISTANCE 1 M Ω
PVG +0.0500
COMPARISON or
DIFFERENTIAL
COMPARISON
EFFECTIVE GAIN X10
Set the Function generator’s output to 50 kHz and 100 mVp-p sine wave and the output connected
to the DA1855A’s +INPUT.
Set the oscilloscope to 50 mV/div (equivalent to 5 mV/div with DA1855A set at X10 GAIN) and
time/div adjusted for 2 to 3 cycles.
Externally trigger the oscilloscope by connecting a cable from the function generator’s output (same
signal as is applied to the DA1855A's +INPUT) or from the Trigger Signal out on the Function
generator to the External trigger input of the oscilloscope.
Under these conditions, the negative peak of the display on the oscilloscope should be very near
center screen. Adjust the value in the Precision Voltage Generator until the negative peak is at
center screen.
Press the VDIFF button. This internally applies the output of the Precision Voltage Generator to a
point within the DA1855A's amplifier that facilitates a true differential offset. The VCOMP light went
out and the OFF light was lighted. In the line under the Precision Voltage Generator display
(COMPARISON or DIFFERENTIAL OFFSET), the COMPARISON light went out and the DIFFERENTIAL
light was lighted. This indicates that the Precision Voltage Generator will now be applied as a
differential offset rather than as a comparison voltage as in the previous exercise. Both the +INPUT
and the –INPUT inputs are now enabled.
The positive and negative peaks of the waveform displayed on the oscilloscope are 10 divisions
above and below (respectively) the center line of the display. Push the button above the digit that is