Stanford Research Systems SR785, Operating Manual And Programming Reference

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4-178 Disk Buffers Menu
SR785 Dynamic Signal Analyzer
Turning the knob will bring up the directory tree display which lists all of the sub-
directories on the disk. Choose a directory with the knob and press [Enter] to make it the
Current Directory.
A directory may be entered using the [Alt] key and the letters associated with each key.
Press [Alt] again to return to normal keypad operation. An error results if the entered
directory does not exist.
New directories are created with <Make Directory>.
Command: FDIR (?) {s}
Load Trace Data (ASCII)
Load ASCII data from the Current File in the Current Directory into an existing Trace.
This is a way to import calibration data from a file into a trace. The trace can then be
used in a user function to calibrate live measurements.
The target trace must already store data of the type and length to be loaded from disk.
The file only contains data points, no measurement information is recalled. The recalled
data simply takes the place of the stored trace data and assumes the trace’s measurement
parameters (Measurement, Averaging, Window, Frequency span) and length.
The ASCII file consists of N pairs of ASCII floating point values. Each pair of values
represents the real and imaginary parts of a single complex data point. Thus, the file
contains 2N floating point numbers. The values are linearly scaled (usually with units of
Vpk).
The first value in the file is N, followed by the real part of the first point, then the
imaginary part of the first point, etc. Each value is delimited by a comma, white space,
tab or carriage return. Traces which are entirely real should store 0.0 as the imaginary
part of every point.
The value of N depends upon the type and length of the target trace. N should be picked
at least as large as the number of points displayed in the trace. If N is specified too small,
the trace will be zero padded. If N is too large, the extra points will be ignored.
For example, the ASCII file for a 400 line FFT might be
400
0.000, 0.500
1.000, 1.500
2.000, 2.500
...
399.000, 399.500
where (0.000, 0.500) is the first complex data point and (399.000, 399.500) is the 400th
data point.