Reference
Probe Cal
This oscilloscope lets you compensate the entire signal path, from probe tip to
digitized signal, to improve the gain and offset accuracy of the probe. By
executing
Probe Cal
on a channel with its probe installed, you can optimize
the oscilloscope capability to make accurate measurements using that chan-
nel and probe.
Run a Probe Cal anytime you wish to ensure that the measurements you
make are made with the most accuracy possible. You should also run a Probe
Cal if you have changed to a different probe since the last Probe Cal was
performed.

Probe Cal vs. Probe Type

Some types of probes can be gain compensated, some can be offset com-
pensated, and some can be compensated for both.
Some probes cannot be
compensated.
If your probe has an attenuation factor of greater than 20X, it cannot be
compensated. If you attempt to compensate such a probe you will get an
error message.
The digitizing oscilloscope cannot compensate probes whose gain and/or
offset errors are too great ( 2% gain and/or 50 mV offset). If these errors
are within specified limits for your probe, you may wish to use another probe.
If they are not within specification, have your probe checked by service
personnel.
NOTE
Probe Cal is not recommended with the P6139A passive probe.
This probe typically has little gain and offset error, and therefore, the
improvement in performance after a Probe Cal is not worth the time
needed to do the Probe Cal. Probe Cal makes significant perfor-
mance improvements when performed with active probes or older
passive probes.
If you are installing an
active
probe, such as the P6205, there are no prereq-
uisites to performing this procedure. Start at step 1.
If you are compensating for a
passive
probe with this procedure you must first
compensate the low frequency response of the probe. First, do steps 1 and 2
below, and then perform the instructions found under
Probe Compensation
on
page 3-110. Then continue with step 3 of this procedure.
Operation