Teledyne LeCroy DA1855A - Manual (Page 36)

DA1855A Differential Amplifier
30 922258-00 Rev A
Following are a few observations on using the differential offset mode (V
DIFF
) of the DA1855A:
• Both the positive and negative inputs (AC, OFF and DC) are enabled and the DA1855A
remains a true differential amplifier.
• The value displayed by the Precision Voltage Generator indicates a waveform’s differential
voltage, with respect to the –INPUT, as it passes through the oscilloscope display’s center
line.
• By using the DA1855A in the differential offset mode and the oscilloscope in a high
sensitivity setting, high resolution voltage measurements can be made.
• The Precision Voltage Generator can be used as a position control which allows the
DA1855A to operate in its most linear region.
Setting up the Oscilloscope without ProBus Interface
Connect a 50 Ω coaxial cable between the AMPLIFIER OUTPUT BNC on the DA1855A rear panel and
the oscilloscope’s input connector. If the oscilloscope has 1 MΩ and 50 Ω input capability, select 50
Ω. If the oscilloscope has only a 1 MΩ input, terminate the coaxial cable at the oscilloscope’s input
with a 50 Ω feed through terminator. It is important that the DA1855A be terminated by 50 Ω.
Set the oscilloscope vertical scale factor to 50mV/div. Set the oscilloscope’s input coupling to GND
or OFF and position the trace to center screen. Do not move the oscilloscope position setting after
this initial set-up. Change the oscilloscope input coupling to DC.
Change the power switch located on the DA1855A's rear panel to 1 (ON) and observe the DA1855A's
front panel indicators. Initially, each indicator light will be ON and the red OVERLOAD indicator will
be ON as well. All segments in the Precision Voltage Generator display will be ON. After
approximately 3 seconds, the DA1855A will return to the settings in effect when the power was last
turned off.
Set the DA1855A as follows:
+INPUT DC
–INPUT OFF
BW LIMIT FULL
GAIN X1
ATTENUATOR ÷10
INPUT RESISTANCE 1 M Ω
PVG +00.000
COMPARISON or
DIFFERENTIAL
COMPARISON
EFFECTIVE GAIN ч10