Oscilloscopes

Standard deviation calculations in PicoScope 5


The PicoScope PC oscilloscope software provides a full range of automatic measurements and calculations. Time-domain measurements include pulse width and peak-to-peak amplitude, while frequency-domain measurements include noise and various harmonic amplitudes. PicoScope can also calculate a number of statistical parameters based on these measurements, such as average, standard deviation, maximum and minimum. We hope you will find many of these features useful. To get you started, here is a brief introduction to the standard deviation feature.

Standard deviation is a measure of the reliability of repeated measurements. If a pulse width measurement is very stable, it will have a small standard deviation, but if the measurement is highly variable, perhaps as a result of noise, then the standard deviation will be larger. Standard deviation, like average, is expressed in the same units as the original measurement. To measure the standard deviation of a pulse width, for example, follow these steps:

  1. Use PicoScope in Repeat trigger mode to capture a repetitive pulse waveform.
  2. Select the ‘Settings | Measurements’ menu option and click the ‘Add‘ button.
  3. Select ‘High Pulse Width’ in the Measurements box and click ‘OK’
  4. A ‘High Pulse Width’ measurement line will appear at the bottom of PicoScope’s scope view, showing the pulse width of the waveform in real time
  5. Return to the ‘Settings | Measurements’ menu option, but this time click the ‘Options’ button.
  6. Select the ‘Average’ and ‘Standard Deviation’ check boxes.
  7. PicoScope will add two columns headed ‘Average’ and ‘Standard’ to the measurement line that you created earlier.
  8. While the scope is running, PicoScope will continually update the average and standard deviation measurements.

You can use the statistics functions with a spectrum view as well as with a scope view, using a similar procedure. If you need help, you can always press [F1] to call up the online user guide. You can also download the manual free of charge from our Technical Library.

Article: KB-178
12 Oct 2007