Teledyne LeCroy DXC100A - Manual (Page 15)

Operator’s Manual
922259-00 Rev A 13
10. +Input X100 LF Compensation
NOTE: Low frequency compensation of the DXC100A probe attached to the
+Input is done by observing a small portion of a large amplitude step. For the
100X probe attenuation, the oscilloscope transient response plays an important
part in determining the correct LF compensation adjustment. The oscilloscope
response should be measured at this point and recorded as a reference
waveform.
The oscilloscope’s transient response error may be determined by connecting
the oscilloscope to a known flat pulse generator (i.e., Tektronix PG506 fast rise
output). Since the DA1855A produces a maximum output of 0.5 volts, apply a
waveform that is stepped from -0.5 volts to 0 volts to the oscilloscope.
Oscilloscope response is recorded at 10mV/div, 10μs/div. The correct
adjustment of the DA1855A produces a waveform most like the recorded
reference waveform, and not necessarily the flattest waveform.
Digital oscilloscopes record and store waveforms nicely. Some users of analog
oscilloscopes mark waveforms on the CRT face using a grease pencil.
a. Set the oscilloscope to 10μs/div and 10mV/div.
b. Press the –Input DC Off button.
c. Set the probe to the 100X position.
d. Connect the +probe to the high amplitude output of the pulse generator
using a 50 Ohm or (preferably) 75 Ohm termination and the BNC to
probe tip adaptor.
e. Press the X10 Gain button.
f. Set the pulse generator amplitude to maximums (5-8V peak).
g. Set the BW Limit to 20 MHz.
h. Adjust C17 (+X100 LF1) and C11 (+X100 LF2) for a response that matches
the oscilloscope response noted earlier. Ignoring any DC offset, the
recorded waveform and this displayed trace should match within 0.1 div.