An instrument to measure and compute the mean and standard deviation of the oscillations of a recording arm
B Hogley · Journal of Scientific Instruments · 1952
An instrument is described which measures the displacement y of the arm of a pen recorder at regular intervals along the recording chart, whilst the chart is being produced. The instrument computes Σ y , and Σ y 2 . Its computing section does not contain a squaring device, but produces the square of a given measurement by means of an interconnected system of Post Office relays. The quantities Σ y , Σ y 2 , and n the number of measurements made, are displayed on Post Office type message registers. The quantities recorded facilitate the calculation of the mean and standard deviation of the pen arm displacement.