Mechano-Magnetic Telemetry for Underground Water Infrastructure Monitoring

Abstract

This study reports on the theory of operation, design principles, and results from laboratory and field tests of a magnetic telemetry system for communication with underground infrastructure sensors using rotating permanent magnets as the sources and compact magnetometers as the receivers. Many cities seek ways to monitor underground water pipes with centrally managed Internet of Things (IoT) systems. This requires the development of numerous reliable low-cost wireless sensors, such as moisture sensors and flow meters, which can transmit information from subterranean pipes to surface-mounted receivers. Traditional megahertz radio communication systems are often unable to penetrate through multiple feet of earthen and manmade materials and have impractically large energy requirements which preclude the use of long-life batteries, require complex (and expensive) built-in energy harvesting systems, or long leads that run antennas near to the surface. Low-power magnetic signaling systems do not suffer from this drawback: low-frequency electromagnetic waves readily penetrate through several feet of earth and water. Traditional magnetic telemetry systems that use energy-inefficient large induction coils and antennas as sources and receivers are not practical for underground IoT-type sensing applications. However, rotating a permanent magnet creates a completely reversing oscillating magnetic field. The recent proliferation of strong rare-earth permanent magnets and highsensitivity magnetometers enables alternative magnetic telemetry system concepts with significantly more compact formats and lower energy consumption. The system used in this study represents a novel combination of megahertz radio and magnetic signaling techniques for the purposes of underground infrastructure monitoring. In this study, two subterranean infrastructure sensors exploit this phenomenon to transmit information to an aboveground radio-networked magnetometer receiver. A flow meter uses a propeller to directly rotate a diametrically magnetized neodymium magnet. A moisture sensor rotates a magnet with a low-power electric motor. Laboratory performance and field tests establish the capabilities of magnetic telemetry for IoT-linked leak-detection sensors. Remote datalogging with encryption demonstrates the viability of integrating sensors and surface receivers into a LoRa wireless IoT network.

Investigation of wireless magnetometer in sensing magnetic field changes at different car direction and speed

“…Low magnetic field detected could be used as a reference for classifying vehicle driving in the opposite direction [3,21] and further applied for traffic surveillance. However, measuring the changes or drift of the flux during different time of the day, temperature [22] and different surfaces [23,8] in detecting vehicle is beyond the scope of the current work.…”

“…Such system may ease the monitoring of traffic at the centrally managed Internet of Things (IoT) system. Subsurface sensor node is always an attractive solution for environment [8] and traffic system [9]. A magnetometer is an electronic device which could measure local earth magnetic field direction in space.…”

Radiation Characteristic of Cloud Based Magnetometer for Vehicle Detection

“…The three modules were designed on a single board, as shown in Figure 1. HMC5883L is a triaxial anisotropic Magnetoresistive sensor with a 12-bit analog-to-digital converter and 1 to 2 o compass heading accuracy [7]. Any distortion on the magnetic sensor would generate a change of data for the x-, y-and z-axis.…”

Metrology in Urban Drainage and Stormwater Management: Plug and pray

“…GSM communication might be the best if there is a need for alarm generation and if the staff in charge of the maintenance do not have smartphones. The emerging LoRaWAN (long range wide area network) protocol has been applied successfully in urban hydrology (Blumensaat et al, , 2019Orfeo et al, 2018).…”