Teledyne LeCroy DXC100A - Manual (Page 11)

Operator’s Manual
922259-00 Rev A 9
DA1855A has no probe coding input, and the wire is not used. Skip to
Step 2.

It is important to use the right hardware to connect the probes to the
test signals. In all cases, the BNC to probe tip adapters are helpful. For
the high frequency adjustments, they are required. CMRR (common
mode rejection ratio) adjustments should be done with both probes
connected to a BNC T (two female BNC and one male BNC connected
together without any matching resistors).

With the DXC100A connected, let 20 minutes pass to allow the DA1855A
to warm up before performing the calibration procedure.
2. +Input X10 DC Attenuation
a. Set the probe to the 10X position.
b. Connect both probes to the BNC T, the BNC T and the DVM to the dc
voltage source.
c. Set the voltage source to 150 volts.
d. Press the V
Comp
button. Measure the dc source with DVM and note the
actual voltage (e.g. 149.821 volts).
e. Set the Precision Voltage Generator to equal the noted voltage (e.g.
149.821 volts) 1
f. Set the oscilloscope to 10mV/div. Press the +Input DC button.
g. Set the BW Limit to 20MHz. Press the X10 Gain Button (to invoke
AUTOBALANCE).
h. Adjust R5 (+X10 DC) to bring the DA1855A output to center screen (0
volts) on the oscilloscope. A 1 division error is equivalent to 10mV out of
150 volts, or 0.0067%, or 67 ppm.
3. X10 DC CMRR
a. Continuing from the previous step, press the –Input DC button.
1 When a large voltage is not available, or when extra precision is desired, monitor the PVG output on the DA1855A rear panel and set
the PVG to exactly one tenth the voltage applied to the probe. As little as 32 volts may be used to calibrate the +probe using this
method. For CMRR, 32 volts is inadequate and a 50 or 60Hz signal of 30 to 90 Vrms is recommended.