User`s guide

Waterfall/Map/MultiSpectrum/Spectrogram Data
Many instrument create multiple scans of data and display them as a waterfall, a map, a multispectrum, or
a spectrogram. In an SDF data file, this appears as multiple scans of a data result.
When this type of data is in the file, the scanData field in the SDF_DATA_HDR for a result is set to
TRUE (1) and the SDF_FILE _HDR indicates that either an SDF_SCAN_STRUCT record or an
SDF_SCAN_BIG record is in the file (or both). The last_scan_index field in either of these records
indicates how many scans of data are in the file.
A scan variable may be:
• A time offset from when the measurement was started
• A scan offset from when the measurement was started
• The RPM when the scan was measured
• The average count when the scan was measured
• The overload when the scan was measured
• Information flags when the scan was measured
The first scan variable is in the SDF_SCAN_STRUCT record. The rest of the scan variables are
in SDF_SCAN_VAR records. Most instruments support only one scan variable, which is in the
SDF_SCAN _STRUCT record.
The HP 89410A and HP 89440A support 4 scan variables as follows:
Scan variable Description
0 (SDF_SCAN_STRUCT) Scan offset from when the measurement was started
1 (SDF_SCAN_VAR) Same as above
2 (SDF_SCAN_VAR) The average count when the scan was measured
3 (SDF_SCAN_VAR) Information flags when the scan was measured (see below)
Information flags for scan variable 3:
Standard Data Format (SDF)
B-40