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Probe Cal
TDS 620A, 640A, & 644A User Manual
19. If desired, repeat this procedure beginning at step 1 to compensate for
other probe/channel combinations. But before you do so, be sure you
take note of the following requirements:
Remember to first low frequency compensate any passive probe you
connect (see
Prerequisites
at the beginning of this procedure).
Remember to connect all but simple passive probes to the oscillo-
scope for a twenty minute warm up before running Probe Cal.
The following topic contains information you should consider when using input
channels that have stored a Probe Cal.
Changing Probes After a Probe Cal
If a Probe Cal has never been performed on an input channel or if its stored
Probe Cal data is erased using the
Re-use Probe Calibration Data
menu
(discussed later), the oscilloscope displays
Initialized
status in its vertical
menu. It also displays initialized whenever you remove a probe from an input.
If you execute a successful Probe Cal on an input channel, the oscilloscope
stores the compensation data it derived in non-volatile memory. Therefore,
this data is available when you turn the oscilloscope off and back on, when
you change probes, etc.
When you install a probe or power on the oscilloscope with probes installed,
the oscilloscope tests the probe at each input. Depending on the probe it finds
on each input, it takes one of the following actions:
If the probe has a complex oscilloscope interface (it can convey additional
information, such as a unique identification number), the oscilloscope
determines whether it is the same probe for which data was stored. If it is,
the oscilloscope sets status to pass; if not, it sets the status to
Initialized.
If a probe has a simple oscilloscope interface, the oscilloscope can usual-
ly determine if it has a different probe attenuation factor than that stored
for the last Probe Cal. It can also determine if the last Probe Cal was for a
probe with a complex interface. If either is the case, the probe installed is
different from that stored for the last Probe Cal. Therefore, the oscillo-
scope sets the status to
Initialized.
If a probe has a simple oscilloscope interface and the probe attenuation
factor is the same as was stored at the last Probe Cal, the oscilloscope
cannot determine whether it is the same probe. Therefore, it displays the
Re-use Probe Calibration data?
menu (see Figure 3-56).
Usage