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37
Calibration Tests and Adjustment
CMRR Test
7 On the oscilloscope, press AUTOSCALE and set the following parameters.
8 On the oscilloscope, measure the peak-to-peak voltage of the channel 1 signal,
then V P-P, then press 1) and record the reading.
V
p-p
(1) = _____________ mV
9 Connect the input of the probe to the test board in the position shown in the
figure below (signal to both inputs).
Figure 2-10
Signal to both input
10 Set the sensitivity to 1 mV/div.
11 After the measurement settles (averaging is complete), record the V P-P
reading.
V
p-p
(2) = _____________ mV
12 Disconnect the probe amp from the test board and measure V
noise pp
on
channel 1.
13 Calculate the CMRR result as follows
14 The result in step 12 should be ≥ 3000, representing a CMRR of 3000:1 or more.
Record the CMRR in the Calibration Test Record.
Menu Selection Setting
TIMEBASE (time/div) 500 ns/div
CHAN 1 (sensitivity)
(input R)
200 mV/div
50 Ω DC
ACQUISITION Sampling Mode
Memory Depth
Sample Rate
Averaging
# of avg
Real Time
Automatic
Automatic
Enabled
32
CMRR
V
pp
1
V
pp
2
V
noisepp
–
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