The WaveRunner 6 Zi scope family, includes a probe calibration function built into each of the input channel’s dialog box. They also include a built in FastEdge waveform that serves as the calibration source. Optionally, there is a probe calibration and deskew test fixture (TF-DSQ) that allows calibration of probe skew, vertical offset and gain.
- Recall the default setup: File pull down > Recall Setup> Recall Default.
- Set the input coupling on Channel 1 to be DC 1 MΩ: Touch or click the channel 1 annotation box>touch or click on the coupling field >select DC 1MΩ. Using the C1 dialog box, set the channel 1 vertical scale to 200 mV/division and zero the vertical offset so that the trace is centered vertically on the display grid. Repeat these steps for all four channels.
- Set up the Aux output to be the Fast Edge signal. Utilities pull down > Utilities Setup >Aux Output Tab>touch or click on Fast Edge. The Fast Edge signal is a 5 MHz, 450 mVp-p, square wave into 50Ω.
- Turn on all four scope channels.
- Set the Display to Single Grid (Display pulldown>Single Grid).
- Set the trigger source to C1 and the trigger level to level to 0 mV.
- Set the Horizontal scale to 1 ns/division using the Horizontal time/division control on the front panel.
- This completes the initial setup. The scope display should be similar to Figure 1.
Connect 3 BNC tee adaptors to the Aux BNC output on the front panel of the scope as shown in Figure 2.
This configuration of the BNC tees will allow you to connect 4 probes to the FastEdge signal from the Aux output.
Connect a 10:1 passive probe to each scope input channel and the other end to one of the BNC tee ports using probe to BNC adaptor.
We are now in a position to deskew all for channels without having to move probes.
With all four channels connected to the FastEdge waveform from the Aux output the scope display should appear as shown in Figure 3.
Open the channel 1 dialog box by touching or double clicking on the C1 trace annotation box. You can also use the Vertical pulldown menu and select Channel 1 Setup. See Figure 4.
Press the Probe Cal button. The Probe Cal dialog box will appear. Select the Cal Source to be the FastEdge. Select C1 to be the the Cal Skew Ref as seen in Figure 5.
The information on the probe calibration dialog is organized so each row represents the information for a given channel and each column represents the calibration information or control for that channel. For each channel, the information and controls provided include:
The channel number in the colored button icon and the probe type that is installed.
A Deskew Only button, which starts the deskew calibration.
The skew correction
A Clear button.
Press the Deskew Only button associated with Channel 2. The scope will begin an automated deskew process (Deskew Wizard) and document the process with a pop up box. Once the skew correction has been computed it will prompt for the user to apply the correction as shown in Figure 6.
Press the apply button. Channel 2 and Channel 1 should now appear to be aligned at the trigger level as shown in Figure 7.
Repeat this process for channels 3 and 4. This should result in all the channels being aligned (Figure 8).
Alternative probe connections
Different probes require different means of connecting to the calibration source. One alternative is the PCF 200 fixture.
The Probe Deskew Fixture (PCF200) is provided as a standard accessory with WaveLink series Platform/Cable Assemblies.
The fixture can be used one of two ways:
For lower bandwidth WaveLink probes (≤ 6 GHz), the fixture may be used to determine the effect of probe input loading on the circuit under test and the probe response to the signal being measured.
The fixture can be used with all WaveLink tips (not at full bandwidth), it may be used as a convenient way to deskew several probes/oscilloscope channels. This can be accomplished in the following ways: Connect a fast edge to one of the inputs. Connect the probe tip(s) to the appropriate connection point. Solder-in probe tips and browser tips may be inserted under the clamping mechanism. Display the probe signals on the oscilloscope screen and use the channel deskew adjust to align them to a common point.
Connect the WaveRunner 6 Zi, WavePro 7 Zi and Zi-A, or WaveMaster 8 Zi and Zi-A fast edge output to one of the inputs. Set the oscilloscope to trigger on the internal Fast Edge source. Set the trigger delay to zero. Now, on the vertical dialog, use the Probe Cal - Cable Deskew button to align one signal/channel at a time to the specified zero delay trigger point (center of screen). Repeat for as many probes as you have connected, each time aligning them to the common point.
Note: The Probe Deskew fixture has an inherent rise time limitation of ~70ps. Deskew of very high frequency signals using WaveLink High Bandwidth Differential Probes may require a faster rise time than this fixture can provide. In this case, utilize one of your signals as a reference point, and then deskew all additional signals to the reference signal.
Figure 10 is an example of a PCF 200 being used to deskew ZD1500 probes on a WaveRunner 640 Zi. The PCF 200 input is connected to the Aux output using a BNC –SMA adaptor. The output of that path is connected to the external trigger input of the WR640 Zi (set to 50 Ohms to terminate the FastEdge Signal). The External input is selected as the Cal Skew Reference.
ZD1500 probes are channels 1 through 3 are deskewed as shown in Figure 11. Note that each probe was deskewed individually to the same reference (ext). Waveforms for channel 1 and 2 were stored in memory traces for visual comparison.
A TF-DSQ fixture is available as a LeCroy probe accessory. The product is used in conjunction with the oscilloscope software to perform probe deskew and DC calibration as shown in Figure 12.
Operation of the TF-DSQ is beyond the scope of this tutorial. Complete details for the use of the TF-DSQ fixture can be found in the TF-DSQ manual available on the LeCroy Website (http://cdn.lecroy.com/files/manuals/tf-dsqom-c.pdf)
This completes the tutorial.