Teledyne LeCroy WaveExpert 100H Operators Manual - Manual (Page 222)

Operator’s Manual
220
WE-OM-E Rev A
Before jitter measurements can be taken, the instrument timebase must be set up properly. Jitter
measurements require the CIS timebase primarily because this timebase allows for pattern locking
-- displaying the signal as a voltage vs. time trace -- and the acquisition speed is maximized (10
MS/s). Jitter measurements are not supported using the sequential timebase. The following steps
should be followed to set up the timebase:
1. Connect the signal to an available sampling module in the scope mainframe of the
appropriate bandwidth.
2. Connect a bit clock, synchronous to the data signal, to the CLK/Prescale input. If a clock is
not available, the optional clock recovery module can be used to supply a clock (see the
section on the PPG-E135 in this manual).
3. Touch the CIS button in the horizontal dialog to activate the CIS timebase.
4. Press the Find Rate button in the Horizontal dialog. The green dot in the Timebase
descriptor label indicates that the CIS timebase has locked to the clock.
5. Verify that the proper bit rate is displayed in the Bit Rate field of the Horizontal dialog. If a
sub-rate clock is being used (½, ¼, etc. of the bit rate), enter the divisor (2, 4, etc.) into the
Ext. Divider control prior to touching the Find Rate control.
6. The default setting of the PLL Bandwidth control is High. This is the normal setting for
most jitter measurements. The low setting is designed for testing very low jitter signals,
down to 10 kHz. The PLL settings are shown in the figure above.