8-74 Command Reference
:MEASure: ARRay: FREQuency: BTBack? CNT-91
8(<array size>)[,(@1)|(@2)]
Frequency Back-to-Back
This is the inverse function of Period Back-to-Back. See below. In STATISTICS
mode measurement time is used for pacing the time stamps. The pacing parameter
is not used in this case. Thus a series of consecutive frequency average measure
-
ments without dead time can be made in order to fulfil the requirements for correct
calculation of Allan variance or deviation.
Parameters
<array size> sets the number of samples.
(@1)|(@2) is the measurement channel:
(@1) means input A
(@2) means input B
:MEASure: ARRay: PERiod: BTBack? CNT-91
8(<array size>)[,(@1)|(@2)]
Single Period Back-to-Back
Every positive or negative zero crossing (depending on the selected slope) up to
the maximum frequency (125 kHz with interpolator calibration ON or 250 kHz with
interpolator calibration OFF) is time-stamped. For every new time stamp the previ
-
ous value is subtracted from the current value, and the result is stored.
In STATISTICS mode the array contains all periods up to the maximum input fre
-
quency (see above). For higher frequencies the average period time during the 4
or 8 µs observation time is stored. So, for higher frequencies the actual function is
rather Period Average Back-to-Back.
The main purpose of this function is to make continuous measurements of rela
-
tively long period times without losing single periods due to result processing. A
typical example is the 1-pps timebase output from GPS receivers.
Parameters
<array size> sets the number of samples.
(@1)|(@2) is the measurement channel:
(@1) means input A
(@2) means input B
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