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Probe Cal
TDS 620A, 640A, & 644A User Manual
1. Install the probe on the input channel on which it is to be used.
2. Power on the digitizing oscilloscope and allow a 20 minute warm-up
before doing this procedure.
3. Press SHIFT UTILITY ➞ System (main) ➞ Cal (pop-up).
4. Look at the status label under Signal Path in the main menu. If the status
does not read Pass, perform a signal path compensation (
Signal Path
Compensation,
page 3-138), and then continue with this procedure.
5. Press the front-panel button corresponding to the input channel on which
you installed the probe.
6. Press VERTICAL MENU ➞ Cal Probe (main).
Your oscilloscope will detect the type of probe you have installed and
display screen messages and menu choices for compensation of
probe gain, offset, or both (see Figure 3-55). The following steps will
have you run probe gain, offset, or both depending on the probe the
oscilloscope detects.
7. If the message on screen is
Probe Offset Compensation
rather than
Probe Gain Compensation,
skip to step 15.
8. Connect the probe tip to PROBE COMPENSATION SIGNAL; connect
the probe ground lead to PROBE COMPENSATION GND.
9. Press OK Compensate Gain (side).
10. Wait for gain compensation to complete (one to three minutes).
When gain compensation completes, the following actions occur:
The clock icon will disappear.
If offset compensation is required for the probe installed, the Probe
Offset
Compensation message will replace the Probe
Gain
Compen-
sation message.
If gain compensation did not complete successfully, you may get a
“Probe is not connected” message (examine the probe connections to
the digitizing oscilloscope, be sure the probe tip is properly installed in
its retractor, etc., and repeat step 9).
If gain compensation did not complete successfully, you may get the
message “Compensation Error.” This error implies that the probe gain
(2% error) and/or offset (50 mV) is too great to be compensated. You
can substitute another probe and continue. Have your probe checked
by service personnel.