Sample averaging
This window lets you select the number of voltage readings to be averaged for each recorded Chart sample value.  Averaging is useful for eliminating background electrical noise, or other short-term variation that may obscure long-term trends.  It may also be used to obtain single integrated readings from long intersample intervals.  Some important aspects of averaging:

  •   When Continuous chart scanning option is selected (A-D menu; available in Chart mode only), all channels are scanned sequentially and continually throughout the sample interval.  The Averaging window is not available, and differences in the number of averaged readings between channels are not possible.  This mode provides a more continuous sampling of each channel than in the 'normal' averaging mode, wherein each sample is sampled for N averages before proceeding to the next channel.  It differs from the 'continuous averaging' option described below in that all channels are scanned continuously, not just the last one.

    As for the normal averaging mode, in continuous scanning mode, the number of averaged readings per recorded sample depends on the number of channels, the sample interval, and the speed of the computer and the A-D converter.

  •   The number of readings that can be averaged depends on the number of channels, the sample rate, the speed of the computer, the absolute value of input voltages (low voltages take slightly longer to read than high voltages), and the conversion type used (power functions take longer to calculate than linear or polynomial conversions).  LabHelper offers a default maximal averaging value, based on the sample interval and the number of channels used (it assumes the same number of samples are averaged for all channels).  You can pick a different number by changing the values in the edit fields.  Remember that if you select a larger number you may slow LabHelper down to the extent that it cannot keep up with the requested sampling rate.  If that happens, it will record data correctly and, when data are saved, will calculate the actual sampling rate.

  •    In Chart mode, all of the channels can be set to can be set to make repeated readings until the time of the next sample by switching the "Continuous averaging (all channels)" button to 'on'.  The program cycles through all the channels in an endless loop until it is time for the next sample (at that point all of the readings are averaged and stored).  In this mode at least one reading is always made.

  •    In Chart mode, the final channel can be set to continue making readings until the time of the next sample by switching the "Continuous averaging (last channel only)" button to 'on'.  In this mode at least one reading is always made.

    NOTE:  sample averaging is automatic if you have selected Oscilloscope plus Chart mode.  In this mode a voltage reading is made from ALL channels when the oscilloscope reading is made.  When the sample interval for chart channels has elapsed, the stored readings for the chart channels are averaged, plotted, and saved.  Thus the number of samples averaged for chart channels is roughly equal to the value:

    chart sample interval / oscilloscope sample interval

    Use of this method simplifies calculations and allows the highest possible oscilloscope sampling rate.

    When you are satisfied, click the 'Selection OK' button.

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