What are the differences between the two frequency measurements that the TPS2000 Series makes?

What are the differences between the two frequency measurements that the TPS2000 Series makes?

Automatic Frequency Measurement

• Method used to make measurement: Reciprocal of the Period measurement. Made over the first complete cycle in the record. Period measured from the first mid-ref crossing to the third mid-ref crossing
• Accuracy (typical): +/- (1 sample interval + 50 ppm x reading + 0.6 ns)
• Resolution: 4 digits

Trigger Signal Frequency Readout

• Method used to make measurement: Provides the user with a means of identifying the frequency of trigger signals with higher accuracy than the Automatic Measurements. Because measurement is averaged over a longer time span than in Automatic Frequency Measurement, the number of stable digits is improved.
• Accuracy (typical): +/-51 ppm including all frequency reference errors and +/-1 count errors
• Resolution: 6 digits
• Counter range: AC coupled, 10 Hz minimum to rated bandwidth
• Frequency counter signal source: Pulse width or edge modes, all available trigger sources. Frequency counter measures selected trigger source at all times, including when oscilloscope acquisition is halted due to changes in run status or acquisition of a singleshot event has completed.
• Pulse width mode: Counts pulses of sufficient magnitude inside the 250ms measurement window that qualify as triggerable events (e.g., all narrow pulses in a PWM pulse train if set to > mode and the limit is set to a relatively small time).
• Edge trigger mode: Counts all pulses of sufficient magnitude
• Video trigger mode: Does not operate in this mode