Jackson Labs PHASE STATION 53100A, Руководство пользователя

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PhaseStation 53100A User’s Manual V1.04 25-Apr-2022 174
/window:<samples>
When the /format:F option is used to acquire a stream of absolute frequency
measurements, each frequency reading is normally derived by subtracting the previous
phase-difference reading from each incoming one and dividing the result by the
reciprocal of the sampling interval. The resulting frequency difference is applied to the
input frequency that was provided explicitly with the /input option or estimated when
the measurement began, yielding an absolute frequency in hertz. This value, in turn, is
logged to the specified file, sent to network clients via TCP/IP, and/or written to the
local console window for diagnostic purposes if the Scroll Lock light is on.
It’s possible to achieve much more accurate frequency readings if the frequency-
difference value is computed over longer periods of time. The default /window:1 value
causes frequency readings to be derived from adjacent pairs of phase-difference
readings, as described above. If you specify a larger value with /window:
n
, the
frequency differences are computed from phase readings separated by
n
sample
intervals (or the number of intervals since the acquisition began, whichever is less.)
In the example below, an attempt was made to measure the actual output frequency
from a DDS whose nominal frequency was set to 10 MHz. The use of /rate:1 yielded one
reading per second at the minimum supported measurement bandwidth of 0.5 Hz. The
DDS clock was derived from the same 10 MHz reference that was supplied to the
TimePod, making this a true “residual frequency” measurement.
Example:
stream timepod.tll /input:10E6 /ref:10E6 /rate:1 /format:F /window:100