SA Mode Sweep Time Acquisition |
The following are definitions:
Zerospan Sweep Time: An exact value representing the time spent performing actual hardware acquisition.
Measurement time: A measure of start to finish hardware work. This includes tuning, acquisition, and processing until a trace is generated.
Cycle Time: The round trip time for an entire measurement including the above measurement time plus display painting, retrace, and any system overhead. This is essentially the time from the beginning of one sweep to the beginning of the next sweep.
For NON-Zerospan measurements, the time that is annotated on the screen is the “measurement time”. As the definition states, this does NOT include overhead between sweeps. As the sweeps get faster, the system overhead becomes a relatively larger part, so that when the fastest non-zerospan sweeps are running (that is a 1 MHz span FFT sweep) the annotation measures about 30 mS but the trace update rate is only about 5 or 6 sweeps per second.
For ZEROSPAN measurements, the time that is annotated on the screen is not measured, it is specified. This means the ACTUAL hardware acquisition time is EXACTLY what you specify. For example, in the default 2 mS sweep time, the hardware acquisition runs for exactly 2 mS. Trace points are interpolated to fill out the default 401 point trace. But there is no way you are going to see 500 sweeps per second (500 * 2 mS = 1 second) because the FieldFox cannot update the display that fast. You still only see about 5 or 6 sweeps per second. The system overhead is really dominating at this speed, taking almost all the measurement time. However, the Swp Acquisition time is indeed exactly 2 mS.