Waveform Averaging

Waveform averaging is a process whereby multiple waveforms are summed together and a mathematical average calculated at each point. This has the result of smoothing out transient signals (e.g. noise), leaving only the data to be tested by the user.

Noise on a waveform

The same waveform after 10 averages

By using averaging on a set of waveforms, noise can be reduced and more precise measurements can be taken.

Enabling Averaging

There are two ways to enable averaging: both methods use slightly different configurations. Averaging can be enabled via the Scan Manager form (in Advanced Mode), or the Scan setup form ( in Basic Mode). Averaging can be enabled via the Board Settings tab of the Digital Oscilloscope. To show the Averaging settings, click on the "Show Advanced" button.

Location of the Averaging controls in Basic Mode

Location of the Averaging controls in Advanced Mode

Averaging via Scan Setup

If using the simple averaging option, the system will divide the currently specified increment by the number of averages n and collect the results, averaging every n results.

Averaging via the Board Settings of the Digital Oscilloscope

If using averaging via the board settings, the system will keep the current increment, but use multitriggering (see below) to generate a burst of n results. The results are then averaged.

Averaging and MultiTrigger

The "MultiTrigger" option tells the A/D board to generate multiple acquisitions whenever a trigger is received. Using this feature, the averaged waveforms can be "clustered" in a smaller region than would occur if simply using the normal trigger.

When active, instead of generating one acquisition per trigger, the A/D will generate a number of acquisitions equal to the number of waveforms to average. A delay between acquisitions can be set using the "Holdoff" field.

Note: The holdoff must be sufficient to collect and process each individual acquisition: thus, if end of the acquisition is at 30 us from the main bang, the holdoff must be at least 30 us + extra for A/D processing time. The system will attempt to compensate for an insufficient holdoff. However if set too low, acquisition errors will occur.

Collecting while Averaging

By using the Scan Manager or the Basic Mode setup window, collecting while averaging is simply a matter of following normal scan procedures. Scan speed may be reduced due to increased processing load if scanning at high resolution.

If scanning using The Board tab from the Digital Oscilloscope, extra care must be taken to ensure that multitrigger and holdoff are set correctly.