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What is Sensus?

Sensus is a ultra-lowpower, Homeassistant-compatible environment and plant sensor. It started as a plant health monitoring sensor but ended up being a more general-purpose environment sensor with optional addons, one of which is the Plant Health Monitoring Addon.

Main Features​

  • Measures Temperature🌡️, Relative Humidity 💧, Illuminance ⛅ and Battery Voltage 🔋
    • 🌱 Additional Plant Addon also adds Soil Temperature and Soil Moisture
  • Homeassistant compatible out of the box, thanks to the BTHome data format 1
  • Transmits data via Bluetooth Low Energy and USB 🔌
  • Compatible with BLE4.0+ adapters
  • 100m of range when transmitting data via Bluetooth 📶
  • Powered either via USB-C or a CR2032 battery
  • Ultra-low power consumption, ~1 year battery life when powered from a high-quality CR2032 battery 2 ⌛
  • RGB status LED 🚦
  • sensus-cli command line interface that can be used to:
    • Log real-time data via USB and save to a CSV file
    • Log real-time data via Bluetooth and save to a CSV file not yet implemented
    • Configure parameters such as time between measurements, Bluetooth name, LED behavior
    • Power-safe firmware updates via USB and BLE 3
    • Read device information such as firmware version and MAC address/serial number
  • Optional magnetic 3D printed case with plexiglass window available

Specifications - Sensus​

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All accuracy related specifications assume the device is functioning within the recommended operating temperature range of -10°C - 45°C (14°F - 114°F)

Operating voltage 1.7V - 3.6V
Supply current (while on battery) 24μA typ.
Operating temperature -10°C - 45°C (14°F - 114°F)
Operating relative humidity any %

Temperature and RH sensor​

Sensor Sensirion SHTC3
Temperature range -40 - 125°C (-40 - 257°F)
Typical temperature accuracy ±0.2°C (±0.36°F)
Maximum temperature accuracy ±0.5°C (±0.9°F)
Humidity range 0 - 100%
Typical relative humidity accuracy ±2%

Illuminance sensor​

Sensor Texas Instruments OPT3001
Measurement range 0 Lux - 83865.6 Lux

Specifications - Soil Probe​

Probe soil moisture sensor​

Sensor Custom RC oscillator
Type Capacitive; non-contact
Measurement frequency 10kHz - 2MHz
Calibration Calibrateable via CLI

Probe temperature sensor​

Sensor Texas Instruments TMP112
Measurement range -40 - 125°C (-40 - 257°F)
Typical accuracy ±0.5°C (±0.9°F)
Maximum accuracy ±1.0°C (±1.8°F)

Commonly asked questions​

Is the device waterproof?​

The soil probe is waterproof, however the main control unit (the rectangular PCB) is not due to the limitations of a 3D printed case. I recommend to exercise caution with the main unit and avoid anything more than light splashes, even though it might be fine.

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I did test the Sensus in outside conditions for long periods of time and with occasional water spraying on the main unit and it still appears to function, however I can't recommend you do the same. You can, but it's on your own risk.

  1. See the official Homeassistant BTHome integration page for more information.↩
  2. Battery life can be increased slightly (or decreased) using the command-line interface to raise (or lower) the time between measurements.↩
  3. BLE firmware updates are coming soon.↩