Fluke CombiScope PM3370B User Manual page 184

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Limitations:
•
The MTB value of 2 ns is only possible for the PM339xB CombiScope
instruments.
•
If SENSe:SWEep:REALtime is ON, the MTB range is from 200 seconds to
250 nanoseconds, and sequential sampling is not guaranteed.
In a similar way, the time value Ts that is associated with a trace sample point can
be calculated from the following expression:
Ts = <sample_index>
where <sample_index> is the point number of the sample in the trace.
After a RST command, the sweep time is 10 milliseconds.
*
Coupled values:
There exists a coupling between programming of the sweep time and the number
of trace points (acquisition length). The coupling is one way, which means that the
sweep time changes if the acquisition length changes. Example:
→
- Send RST
*
The number of trace points is 512.
→
- Send SENSe:SWEep:TIME .04
The sweep time is specified at 40 ms. The MTB becomes (0.04
which is rounded to 4 ms. The result of this is that the sweep time is changed
to (0.004 511) / 50 = 0.04088 seconds.
*
→
- Send TRACe:POINts CH1,4096
The number of trace points becomes 4096 instead of 512. The result of this is
that the sweep time becomes 8 times as high.
Note: When the magnifying factor is
the total acquisition length are visible on the display. So, if the acquisition
length is 4096 samples, only 1/8 of the trace is displayed on the screen.
Example:
→
Send SENSe:SWEep:TIME?
←
Read <sweep_time>
→
Send TRACe:POINts? CH1
←
Read <acq_length>
MTB = 50 * <sweep_time> / (<acq_length> - 1) Calculates the MTB
PRINT "Main Time Base ="; MTB; "s/div"
Front panel compliance:
The SENSe:SWEep:TIME command is the remote equivalent of the front panel
TB MODE "s VAR ns" keys.
SENSe:SWEep:TIME / (TRACE:POINts - 1)
*
1, always 500 sample points (10 x 50) of
*
COMMAND REFERENCE
*
Requests sweep time
Reads sweep time
Requests nr of trace points
Reads number of trace points
Prints the MTB
50) / (511),