HP 54620A, User'S And Service Manual

Page: 143 / 243

Best Probing Practices
Because of the variables L , di , and dt , you may be unsure how much margin
is available in your measurement setup. The following are guidelines for good
probing practices:
•
The ground lead from each channel group (0-7 and 8-15) should be
attached to the ground of the circuit under test if any channel within the
group is being used for data capture.
•
When capturing data in a noisy environment, every third probe’s ground
should be used in addition to the channel group’s ground.
•
High-speed timing measurements (T
R
< 3 ns) should make use of each
probe’s own ground.
When designing a high-speed digital system, you should consider designing
dedicated test ports that interface directly to the instrument’s probe system.
This will ease measurement setup and ensure a repeatable method for
obtaining test data.
Ensuring Accurate Measurements
Probing the Circuit Under Test
142