Monthly Archives: December 2021

Real Time Coastal Wave Monitor

WiSense developed this prototype for a university in the US. The prototype uses a high resolution pressure sensor to determine wave height and report the same to the cloud in real time. This is intended to replace currently available instruments which log data but do not have radio connectivity to report the data in real time.

We used a LTE CAT1 modem to report the sensor data sampled at 16 Hz. LTE CAT-M and LTE NB-IOT radios are meant for applications which need to communicate infrequently like a water meter which sends a small message every hour or just once every day.

As can be seen in the pics below, the sensor node has two distinct parts – the sensing module and the comms module which are connected by a cable which can be up to 50 meters long.

Sensing Module

  • Analog pressure sensor with exposed diaphragm
  • Signal conditioning circuitry
  • RS-485 Transceiver
  • Waterproof Stainless steel enclosure
  • Waterproof cable connection

Comms Module

  • STM32 Microcontroller
  • RS-485 Transceiver
  • LTE CAT1 Radio
  • Weather proof LTE Antenna
  • LI-Po battery
  • Atmospheric pressure sensor
  • IP67 Enclosure
  • Provision for external power supply
  • Waterproof cable connection

The connecting cable has three functions.

  • As a tether
  • Conveys power to the sensing module.
  • RS-485 data link (Differential signaling suitable for long distances)

Sensor in action (Wilmington, NC)
Comms module

We designed the water-proof stainless steel enclosure from scratch. Here are some 3D renders of the enclosure. The enclosure was machined in Bangalore.

Machine enclosure with sensor and cable

Sensor data showing high and low tides. Top graph – sensor data. Bottom graph – off the shelf logger data

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