Noise and filtering

A reading is a number plus a distribution. Measuring the distribution, averaging it down, filtering in real time, throwing out the readings that are wrong, and paying for all of it in lag.

Module U4University7 lessons

1. U4.1 A reading is a distribution Mean, standard deviation, and what one number from a sensor is actually telling you.
2. U4.2 Averaging The square root of n, why it stops paying, and what it costs in time.
3. U4.3 The low pass filter A moving average, then the exponential filter that does the same job in one line and no memory.
4. U4.4 Outliers Some readings are not noisy, they are wrong. The median, and gating on what you expected.
5. U4.5 The price of filtering Every filter delays. Measuring the delay, and what it does to a loop closed around it.
6. U4.6 Choosing the filter Matching the cut-off to the signal you care about, by measurement rather than by taste.
7. U4.7 Project: hold the gap Sit 25 cm from a wall, steadily, on a depth sensor that is 3 cm noisy.