Introduction

Empty tanks surprise farms, homes, and estates when nobody checked yesterday. A Raspberry Pi with an ultrasonic sensor can measure freeboard continuously and push data to a cloud dashboard so you know litres left and roughly how many days remain.

Architecture

The sensor measures distance. The Pi runs the WellSenseOS agent. The cloud stores readings and powers analytics, alerts, and multi-device management.

Required components

Raspberry Pi 3B+, 4, or 5 with power supply
HC-SR04-class ultrasonic module (waterproof housing recommended outdoors)
Wiring / breadboard or PCB; level shifting if required by your sensor voltage
Weatherproof mount above the water surface
Network access (typically Wi‑Fi) at the install location

Exact SKUs are not mandated — choose parts that match voltage and environmental needs.

Sensor wiring (conceptual)

Ultrasonic modules expose trigger and echo lines plus power and ground. Many 5V sensors need careful interfacing with 3.3V Pi GPIO — use level shifting where datasheets require it. Follow your module’s documentation; incorrect voltage can damage the Pi or sensor.

Sensor placement

Aim perpendicular to a calm water surface
Respect minimum sensing distance (dead zone)
Stay within maximum rated range
Avoid tank walls, pipes, ladders, and foam in the acoustic cone
Manage condensation on the transducer face

Measuring distance

Ultrasonic sensors emit a pulse and time the echo. Distance is proportional to time of flight (accounting for the speed of sound). Temperature affects speed of sound; outdoor installs may show small seasonal bias.

Converting distance to water depth

water_depth = tank_height - measured_distance

tank_height is the distance from the sensor mounting plane to the tank floor (or empty reference). Measure carefully during install.

Converting water depth to volume

Rectangular tank:

volume = length × width × water_depth

Vertical cylinder:

volume = π × (diameter / 2)² × water_depth

Use consistent units (e.g. metres → cubic metres → litres). Try the tank volume calculator for quick checks.

Calibration

Empty and full reference distances
Dead-zone awareness near the sensor
Filtering / smoothing noisy samples
Verify volume against a known fill when possible

Sending data to WellSenseOS

Flash the WellSenseOS Pi image, complete SoftAP provisioning with Wi‑Fi and account credentials, and assign the device to a well/tank in the portal. Details: setup guide and Pi hardware page.

Dashboard and alerts

The portal shows live level, history, and analytics. Configure low-level alerts so you act before empty. See water tank monitoring for the product story.

Days remaining

Usage history estimates remaining days: current volume divided by recent daily consumption. Variance is normal — treat estimates as guidance.

Multi-tank monitoring

Repeat the edge install per tank (or site) and manage them under one organisation. Farms often start here: farm monitoring.

Troubleshooting

Unstable readings — foam, turbulence, echo multipath; improve aim and filtering
No echo — wiring, power, out of range, or absorbent surface
Condensation — drip shields / waterproof transducers
Wi‑Fi problems — signal at install; SoftAP retry if provision failed
Wrong volume — tank dimensions or empty/full calibration