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P77DESKEW Fixture Instructions
Check the calibration
status
www.tek.com
Copyright © Tektronix
*P077126300*
077-1263-00
The P77DESKEW probe deskew fixture provides an edge source to time-align
(deskew) signals at the inputs of P7700 Series probes. The fixture provides a
means to deskew two probes at the same time. The probe and the fixture are
powered by one of the USB ports of the oscilloscope; a USB cable (Tektronix part
number, 174-6919-xx) is included with the fixture.
For performing the deskew procedure, Tektronix recommends using a
DPO/MSO70000C/70000DX series oscilloscope.
Connectors on the fixture accept solder tips that are available for the P7700 Series
probes. The fixture can also be used to deskew probes with browser accessories.
CAUTION.
The probes used with the deskew fixture are ESD sensitive. To avoid
damaging the probes, perform these procedures at an antistatic workstation, with
an anti-static wrist strap while observing proper ESD practices. Refer to your
probe user manual for the anti-static information.
For best performance, you should check the calibration status of the oscilloscope
before performing the deskew procedure. If the oscilloscope requires calibration
or the probe requires compensation, perform these steps before deskewing the
probes. Refer to your oscilloscope manual for instructions on performing the
oscilloscope calibration procedures.
To check the calibration status of the probe, perform the following steps:
1. Select Probe Cal... from the Vertical menu.
2. Select the channel to which the probe is attached and then check the Probe
Status readout. There are three possible values for the status:
Initialized. The probe has not been calibrated on the selected channel;
perform the DC probe calibration procedure.
Compensated. The probe has been calibrated on the selected channel.
Fail. The probe has not been calibrated; repeat the procedure.
If the test continues to fail, troubleshoot the problem; do not continue with the
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Summary of Contents for Tektronix P77DESKEW
- Page 1 (deskew) signals at the inputs of P7700 Series probes. The fixture provides a means to deskew two probes at the same time. The probe and the fixture are powered by one of the USB ports of the oscilloscope; a USB cable (Tektronix part number, 174-6919-xx) is included with the fixture.
- Page 2 P77DESKEW Fixture Instructions Deskew procedure The deskew function compensates for signal delays that occur between probes due to different tips or cable lengths. The oscilloscope deskew feature applies deskew values after it completes each acquisition. The deskew values do not affect logic triggering.
- Page 3 P77DESKEW Fixture Instructions 6. For P77STFLXA or P77STCABL tips, connect the tips to the fixture as follows: a. Locate the Port1 plastic clamp on the fixture and press down on the spring-loaded clamp. Insert one of the probe tips in the direction shown in the following figure, and release the clamp so that the tip locks in place.
- Page 4 P77DESKEW Fixture Instructions Insert the TekFlex connectors into the P77BRWSR tips and then continue with the following steps: a. Press one of the P77BRWSR tips against one of the pairs of signal traces on the B (Port4) side of fixture board edge, located between the Port1 and Port2 clamps.
- Page 5 P77DESKEW Fixture Instructions The following figure shows an example of using the hands-free accessories with two browsers connected to the deskew fixture. Figure 4: Connecting the hands-free accessories and P77BRWSR to the deskew fixture 8. Adjust the oscilloscope to display a stable waveform or push the Autoset button.
- Page 6 P77DESKEW Fixture Instructions 15. Adjust the horizontal SCALE and horizontal POSITION so the differences in the channel delays are clearly visible. The waveforms on the screen should look similar to the following figure (note the delay between the two edges): Figure 5: Signal delay between two channels 16.
- Page 7 P77DESKEW Fixture Instructions 18. Adjust the deskew time for that channel so that its signal aligns with that of the reference channel. When the signals are aligned they should look similar to the following figure: Figure 6: Aligned signals, no delay 19.
- Page 8 P77DESKEW Fixture Instructions P77DESKEW Description Specification specifications Input impedance 50 Ω ±2% Fast Edge signal A & B input connectors Maximum input signal 4.6 V Time delay (Typical) ≤5 ps A to B (differential signal path) Port1 to Port2, or Port3 to Port4 ≤10 ps...
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