Capacitive Soil Moisture Sensor — Corrosion-Resistant Analogue Module
This capacitive soil moisture sensor measures soil water content by detecting changes in the dielectric constant of the soil surrounding the sensor probe, without current flowing through the soil. Unlike resistive sensors with exposed electrodes, the capacitive design does not corrode over time — the sensing electrodes are embedded under a protective coating and never contact the soil directly. Output is a 0–3.3V analogue voltage that connects directly to any ADC pin on an Arduino or ESP32.
- Capacitive sensing — no corrosion, works for years in soil
- Analogue output — 0–3.3V, reads on any ADC pin
- 3.3V–5V supply — compatible with Arduino, ESP32, Raspberry Pi
- Corrosion-resistant coating — suitable for permanent outdoor burial
- No soil contact on electrodes — reliable long-term readings
| Specification | Value |
|---|---|
| Sensing method | Capacitive (no exposed electrodes) |
| Output | Analogue voltage (0–3.3V) |
| Supply voltage | 3.3V – 5V DC |
| Output range | Dry soil ~2.8V, wet soil ~1.2V (calibrate per soil type) |
Why is capacitive better than resistive for soil moisture?
Resistive sensors pass a current through the soil via exposed metal probes. That electrolysis corrodes the probes within weeks to months of continuous use in moist soil. Capacitive sensors have no exposed conductors — the sensing element is fully encapsulated — so they remain functional for years in permanently buried applications.
How do you calibrate the soil moisture reading?
Record the raw ADC value with the sensor in completely dry soil (maximum value) and in water (minimum value). Map these two endpoints to 0% and 100% moisture using the Arduino map() function. Soil type affects the absolute values — clay soils read differently from sandy loam at the same moisture content.
Best for
Automatic plant watering systems, greenhouse irrigation controllers, field soil moisture logging, ESP32 garden monitors, smart pot sensors, hydroponic media humidity sensing, and any long-term outdoor soil monitoring application where resistive sensors would corrode.
Why Kunkune
Shipped from UK stock. 60-day returns, no minimum order. Fast Royal Mail delivery.
For temporary use or classroom experiments where longevity is not a concern, the resistive soil moisture sensor is the lower-cost option.
Buying in bulk? For orders of 10+ units, contact us for trade pricing.
