|HY-SR04 is a widely available ultrasound ranging module. It
consists of two 40 kHz Piezo crystals, one acts as a transmitter and
other as a receiver, and some electronics circuitry to measure the
time interval between a burst of sound transmitted and the echo
The four pins are the power supply, ground, trigger and Echo. This module can be connected to ExpEYES-17 as shown in the schematic, to measure distance between the module and the reflecting surface, with an error less than 3mm. This can be used to design several experiments in mechanics.
When a mass suspended on a spring is made to oscillate, the period of oscillation is given by T = 2 * pi * sqrt( m/k), where m is the mass and k is the spring constant. We can measure the period of oscillation by measuring the distance to the moving mass as a function of time. The distance versus time graph is fitted with a sine function to calculate the frequency. The photograph below shows a metal plate suspended on a spring and the SR04 facing it from the bottom. The distance to the oscillating plate is measured for 5 seconds and the data is fitted to a sine function.A video of the experiment is HERE.