Teledyne LeCroy Zi Oscilloscope Synchronization ProBus Module (Zi-8CH-SYNCH) - Manual (Page 9)

Instructions
918246‐00‐RevA 9
Deskewing Master and Slave Channels
Deskew Theory of Operation
Deskewing is an adjustment of waveform data point occurrences on the screen. Deskewing is an operation to
correct the times waveforms are displayed on the screen, mainly to account for propagation delays through
probes and cables, and transfer times from the Slave to the Master oscilloscope. When considering skew, there
are two important things to consider:
• The relative skew between two channels.
• The absolute skew from the zero time reference (the trigger point).
Two channels are properly deskewed relative to each other when the difference between the deskew values
entered for each channel aligns an edge occurring at the same time and applied to both channels. A channel is
properly deskewed in an absolute sense when an edge is applied to the channel, the oscilloscope is triggered on
the edge, and the edge appears such that the trigger threshold crossing appears at the trigger delay, which is the
zero time reference on the oscilloscope screen.
Probes or cables are deskewed one at a time relative to a reference such that the resulting calibration deskews
each probe relative to every other probe or cable.
The WaveMaster 8 Zi has a built‐in fast edge SMA output. This edge may be used as a common deskew
reference edge, and output to either the SMA power splitter (provided) and then to cables connected to the
oscilloscope channels, or to the PCF‐200 Probe Deskew Fixture provided with many LeCroy probes (if probes are
used in your measurements). Or, users can provide a fast edge signal of their own. Regardless, the exact cable or
probe setup, and exact V/div range used in actual signal measurements should be used in the deskew procedure
to ensure the most accurate and repeatable results.
Note: The exact cable setup you plan on using for actual measurements from step 6 of Signal Connections (on
page 4) must be the same setup used along with the cable splitter for the following deskew procedure for
Master and Slave oscilloscope channels.
During a deskew procedure when using the Zi‐8CH‐SYNCH, the Master and Slave oscilloscopes must first be
deskewed with respect to each other using a common reference edge. This establishes a channel + probe/cable
reference point within both the Master and the Slave oscilloscopes. This same reference point is then used to
deskew all channels within each oscilloscope. Typically, the deskew values required are very small, but it is good
engineering practice to verify proper deskew and adjust as needed.
PLEASE NOTE THE FOLLOWING:
• If you're using probes on your input signals, be sure to include them in your deskew measurements.
• When providing your reference signal for deskewing signals, make sure it matches the appropriate V/div
range you plan on using for your actual measurements.
Creating Master and Slave Deskew Channel References
Use the following procedure to first establish a deskew signal reference between C2 on the Master and C2 (or
the relabeled C6) on the Slave oscilloscope.
1. Set up the Zi‐8CH‐SYNCH to trigger in Periodic mode.
Note: In Periodic mode you can only deskew by acquiring A SINGLE ACQUISITION at a time.