:ACQuire:SMODe

:ACQuire Commands

Command Syntax

:ACQuire:SMODe  {NORMal | AVERage}

Query Syntax

:ACQuire:SMODe?

Description

Sets the acquisition sampling mode:

  • NORMal — Individual acquisitions are displayed and measured.
  • AVERage — Acquisitions are averaged. Status information at the top of the display (just below the memory bar) shows how many waveforms have been averaged. :ACQuire:SINGle (for making a single acquisition) and :ACQuire:RUN (for making continuous acquisitions) work normally. Until the specified number of waveform averages (see :ACQuire:COUNt) has been acquired and averaged (also known as the terminal count), channel status and measurements on averaged waveforms are questionable.

Use acquisition averaging in the following instances:

  • Use only with repetitive waveforms.
  • Use to eliminate random noise.
  • Use to improve vertical resolution.
  • Use to improve measurement repeatability.

Do not use acquisition averaging for:

  • Non-repetitive waveforms, as very inaccurate results can occur.
  • Improperly triggered waveforms, as the input waveform may be asynchronous to Infiniium and will average to zero over time even though a non-zero input waveform is being measured.

When acquisition averaging is on, waveforms are acquired from multiple data acquisitions and then averaged together, point by point. The noise sources can average to zero over time while the underlying waveform is preserved. The effective resolution of the displayed waveform increases as more acquisitions are averaged together, provided that the input waveform is repetitive and has a stable trigger point. This improves the stability of both the display and waveform measurements.

When acquisition averaging is selected, use the :ACQuire:COUNt command to set the number of waveforms that you want to use in the calculation. You can enter a value between 2 and 1M. The default value for the number of averages is 16.

For acquisitions up to the specified number of acquisitions to be averaged (for 1 ≤ n < M), the following formula is used to calculate the average for each data acquisition, point-by-point:

After terminal count is reached (n ≥ M), this formula is used to calculate the average or each data acquisition, point-by-point:

where:

  • Aven = the average sample value.
  • n = the current average number.
  • M = Number of Waveforms control setting (terminal count).
  • Si = the ith sample (for the nth sample, Si = Sn).

Example Command Sequence

This sequence of commands selects the averaging acquisition sampling mode and specifies that 32 waveforms/acquisitions be averaged to result in the averaged waveform.

:ACQuire:SMODe AVERage
:ACQuire:COUNt 32