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GB1400 User Manual 2-35
B. Locate the controls in the OUTPUT box of the Generator. Adjust the Data
amplitude and offset as follows:
Caution: Adjust only the DATA signal. Do not change the CLOCK signal.
Set this parameter …to this value …using this procedure.
DATA amplitude. 0.50 volts Press the DATA key. The LED within the switch
should be lit.
Press AMPLITUDE up/down keys until data
amplitude is set to 0.50V.
DATA baseline offset -0.25 volts Press BASELINE OFFSET up/down keys until
data baseline offset is set to -0.25V.
If you examined this output data signal (voltage vs. time) on a scope, it would
look similar to:
+0.25 ←←
Maximum Level
↑↑
+0.00
0.5 V
←←
Optimum Threshold
↑↑
amplitude
-0.25
↓↓
←←
Minimum Level
Voltage ↑↑
-0.50
time →→
-0.25 V
data offset
best value to use for THIS data
threshold is ~0.00 Vdc ++ 0.05 Vdc
You will now be manually adjusting the data input threshold for the GB1400
Analyzer. Locate the controls in the PATTERN box of the Analyzer. Make sure
F2 and F3 are turned OFF. These switches are used when adjusting
CLOCK or REF DATA input parameters.
C. Locate the controls in the INPUT box of the Analyzer. Verify that the
Analyzer THRESH LED is turned ON. This allows manual adjustment of the DATA
Input threshold. The threshold for the selected signal (clock or data) is shown on
the bottom line of the Analyzer’s alpha-numeric status display. Using the INPUT
UP/DOWN keys, adjust this threshold and confirm the following actions:
Note: The BER display on the Analyzer can be set to totalize, window, or test
modes. When in the totalize mode, a small ∞∞ (infinity) symbol will be displayed
before the BER error rate. Use totalize mode for this tutorial exercise. Press the
ERROR DETECTION DISPLAY key several times to setup the analyzer for totalize
mode..