Fluke PM-3384B Coupled values, Requests sweep time, Reads sweep time, Requests nr of trace points

4 - 84 COMMAND REFERENCE

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> * SENSe:SWEep:TIME / (TRACE:POINts - 1)

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 * 50) / (511), 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 *1, always 500 sample points (10 x 50) of 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?	Requests sweep time
Read ← <sweep_time>	Reads sweep time
Send → TRACe:POINts? CH1	Requests nr of trace points
Read ← <acq_length>	Reads number of trace points

MTB =	50 * <sweep_time> /	(<acq_length> - 1) Calculates the MTB
PRINT	"Main Time Base =";	MTB; "s/div"	Prints the MTB

Front panel compliance:

The SENSe:SWEep:TIME command is the remote equivalent of the front panel TB MODE "s VAR ns" keys.