15 Programming Examples
360 U8480 Series Programming Guide
Frequency Sweep Operation
The frequency sweep feature is used to perform measurements in which the input
signal varies in frequency. You will be required to specify the start frequency, stop
frequency, and step frequency. The start frequency and stop frequency represent
the start and stop sweep frequencies respectively. The step frequency represents
the number of triggers of equally-spaced frequency intervals between the start
and stop frequencies, inclusive of the start and stop frequencies.
In frequency sweep, the algorithm automatically selects the frequency table as
reference according to the current signal and calculated frequency. The frequency
sweep feature is to be used with an external trigger. When you send a trigger to
the U8480 Series, it will then acquire a measurement. There is a maximum buffer
of 250, which means that you can capture a maximum of 250 readings in the
frequency sweep mode. You can set the filter length for each measurement.
For example, if the filter length is set to 128, the U8480 Series will take 128
readings and perform averaging to acquire one reading for the frequency sweep.
To check if the frequency sweep operation has completed, first of all, you need to
enable the OPC feature by issuing the *OPC command. When the *ESR? query is
issued for the first time, the returned value will not be 0. However, when the
*ESR? query is issued for the second time, its returned value will be cleared to 0. If
the subsequent *ESR? query returns a 1, this indicates that the frequency sweep
operation has completed.
The following programming sequence example performs a frequency sweep.
Enabling the OPC feature will cause the OPC bit in the ESR to be set when the
frequency sweep operation has completed. If the OPC feature is not enabled, the
OPC bit in the ESR will not be set when the frequency sweep operation has
completed.
-> TRIG:SOUR EXT // Sets the external trigger source required for
the frequency sweep operation.
-> TRIG:SLOP POS // Sets the U8480 Series to accept an external
positive-edge trigger.
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