Innovative cost-effective pendulum tiltmeter based on the moiré technique

Abstract

A newly constructed pendulum tiltmeter has been described based on the moiré technique, which is specified as a series of dark and light patterns configured by the superposition of two regular gratings. This tiltmeter chiefly consists of two frames that can move with respect to each other, and tilting movements are recorded by using the moiré technique. Double similar gratings are attached to the frames. The gratings are installed in parallel, having no physical contact, so that their lines make a small angle with respect to each other. A diode laser beam passes through the formed moiré pattern, and a narrow slit then hits on a light detector. Due to external stress and making a tilt or incline in the moiré tiltmeter, one of the gratings is displaced respect to the other one, leading to the moiré fringe movement. So, the light intensity on the detector changes and is registered as the output voltage. A digital signal processor samples the voltage and generates a record of the tiltmeter. The recorded signal can be used to measure the tilt. We have investigated the experimental results of the tiltmeter, and the outcomes show that the sensor is quite viable. In total, the proposed tiltmeter is cost-effective, easy to install, and able to detect tilts of the order of 0.00001 rad. It is also insensitive to electromagnetic noise and environmental conditions, such as temperature fluctuations. Therefore, the applications of this device vary from civil engineering and geological studies to industrial monitoring and experimental ones.