Low-Cost Depth Sensing Module For Deep-Water Instruments

This project presents the design and validation of a low-cost depth sensing
module for deep-sea instruments, offering a pressure-tolerant, modular al-
ternative to commercial depth sensors that cost 10–20× more. The system
was developed in collaboration with the Woods Hole Oceanographic Insti-
tution to meet a 2,000-meter depth requirement while remaining affordable
and mechanically simple.

The sensor uses a compressible water-filled cavity and a magnetically
tracked piston, converting hydrostatic pressure into linear displacement. This
displacement is measured by an array of Hall effect sensors, interfaced with a
Raspberry Pi Pico microcontroller, and encapsulated in a waterproof epoxy-
potted housing. All critical components were designed to be manufactured
with basic tools and consumer-grade 3D printers.

Key accomplishments include: (1) deep-water survivability: the second
prototype withstood 230 bar—exceeding the 200 bar design spec by 15%;
(2) physical modeling accuracy: magnetic field simulations were fitted to
Hall effect sensor data with R2 ≥0.997; (3) modular design: system com-
ponents were separated into pressure-tolerant and pressure-equalized zones,
simplifying packaging and improving reliability.

This work demonstrates the feasibility of a sub-$60, reusable, and inte-
grable depth sensor for scientific and autonomous underwater vehicles, with
future improvements aimed at full RS-232 compliance, improved calibration,
and UAV platform deployment