Digital Channels 6Keysight InfiniiVision 2000 X-Series Oscilloscopes User's Guide 105In addition to the common mode voltage,longer ground returns also degrade thepulse fidelity of the probe system. Rise time is increased, and ringing, due to theundamped LC circuit at the input of the probe, is also increased. Because thedigital channels display reconstructed waveforms, they do not show ringing andperturbations. You will not find ground problems through examination of thewaveform display. In fact, it is likely you will discover the problem through randomglitches or inconsistent data measurements. Use the analog channels to viewringing and perturbations.Best Probing PracticesBecause of the variables L, di, and dt, you may be unsure how much margin isavailable in your measurement setup. The following are guidelines for goodprobing practices:• The ground lead from each digital channel group (D15–D8 and D7–D0) shouldbe attached to the ground of the device under test if any channel within thegroup is being used for data capture.• When capturing data in a noisy environment, every third digital channel probe'sground should be used in addition to the channel group's ground.• High-speed timing measurements (rise time < 3 ns) should make use of eachdigital channel probe's own ground.When designing a high-speed digital system, you should consider designingdedicated test ports that interface directly to the instrument's probe system. Thiswill ease measurement setup and ensure a repeatable method for obtaining testdata. The 01650-61607 16-channel logic probe cable and the 01650-63203termination adapter are designed to make it easy to connect to industry-standard,20-pin board connectors. The cable is a 2 m logic analyzer probe cable, and thetermination adapter provides the proper RC networks in a very convenientpackage. These parts, as well as the 1251-8106 20-pin, low-profile, straight boardconnector, can be ordered from Keysight Technologies.
