MQ-S2
Soil Moisture & Temperature Sensor
with RS485 Modbus
Overview
MQ-S2 is an economical soil moisture and temperature sensor designed for smart agriculture, precision irrigation, and soil monitoring. It uses Frequency Domain Reflectometry (FDR) technology to measure soil volumetric water content (VWC) accurately. With RS485 Modbus-RTU output, wide voltage supply, and IP68 protection, MQ-S2 is an ideal soil sensor for long-term burial and continuous field monitoring.
Key Features
- Soil Moisture & Temperature in One Probe — Measures VWC 0-100% and temperature -50~50°C.
- FDR Technology — High-frequency domain reflectometry for stable and accurate soil moisture readings.
- RS485 Modbus-RTU Output — Standard industrial protocol, easy integration with irrigation controllers and data loggers.
- IP68 Rated — Fully sealed for long-term burial and outdoor use.
- Wide Voltage Supply — 5-28V DC input, compatible with most agricultural power systems.
- Durable Construction — ABS housing, 316L stainless steel probes, XL01 polyurethane shielded cable.
- Anti-Interference Design — Cut-off frequency interference design for reliable readings in the field.
- Compact & Easy to Install — Small size, lightweight, suitable for multi-depth soil moisture monitoring.
Technical Specifications
| Item | Specification |
|---|
| Model | MQ-S2 |
| Measurement Parameter | Soil volumetric water content (VWC), soil temperature |
| Moisture Range | 0-100% vol |
| Temperature Range | -50~50°C |
| Output Signal | RS485 (Modbus-RTU protocol) |
| Supply Voltage | 5-28V DC |
| Moisture Accuracy | ±5% vol (soil-specific calibration recommended) |
| Temperature Accuracy | ±2°C |
| Resolution | 0.1% |
| Response Time | ≤5Hz |
| Working Current | ≤40mA |
| Long-term Stability | ±3% FS/year |
| Repeatability | 3% vol |
| Medium Requirement | Low salinity soil (EC < 1 dS/m) |
| Protection Rating | IP68 |
| Operating Temperature | -40~85°C |
| Housing Material | ABS engineering plastic |
| Probe Material | 316L stainless steel |
| Cable Material | XL01 polyurethane, Φ5 shielded cable |
| Weight | Approx. 190g |
| Dimensions | See drawing (probe length 60mm, body 72mm) |
Wiring & Connection
RS485 4-wire connection:
| Wire Color | Definition |
|---|
| Red | V+ (Power Positive) |
| Blue | V- (Power Negative) |
| Yellow | A (RS485 A) |
| White | B (RS485 B) |
Connection notes:
- Use shielded twisted-pair cable, minimum 0.3mm².
- Keep RS485 cable away from strong power lines.
- Connect the shield layer to ground.
- For long RS485 buses, add 120Ω termination resistors at both ends.
- Default Modbus address: 01. Data format: 9600, N, 8, 1.
Modbus-RTU Communication
MQ-S2 follows standard Modbus-RTU protocol:
- Function 03: Read data
- Function 06: Write settings
- Default address: 01
- Baud rate: 9600
- Data format: 9600, N, 8, 1
Example reading:
- Moisture output: 0-1000 corresponds to 0-100% VWC.
- Temperature output: 0-1000 corresponds to -50~50°C.
Typical Applications
- Smart irrigation systems
- Precision agriculture
- Soil moisture monitoring
- Greenhouse and nursery management
- Orchard and vineyard irrigation
- Soil and water conservation monitoring
- Agricultural IoT and data acquisition
Installation Guidelines
- Insert the sensor vertically into the soil at 90 degrees. Do not shake or force the probe.
- For multi-layer soil moisture monitoring, insert sensors horizontally at different depths.
- Avoid hard soil clods, stones, or metallic objects near the probe.
- Do not install the sensor at the very surface (5cm depth), as readings may be affected by air and surface conditions.
- Keep the sensor and cable away from high-voltage equipment, VFDs, motors, and strong electromagnetic interference.
- After installation, backfill soil in layers to maintain consistent soil bulk density.
Calibration
MQ-S2 is factory-calibrated for loam soil with default accuracy of ±5% vol. For higher accuracy in specific soil types, soil-specific calibration is recommended. Users can perform calibration using the oven-drying method or contact iMaigg for calibration service.
FAQ
Q1: What does MQ-S2 measure?
A: It measures soil volumetric water content (VWC) and soil temperature.
Q2: What is the output signal?
A: RS485 Modbus-RTU.
Q3: What is the protection rating?
A: IP68, suitable for long-term burial.
Q4: What is the moisture range and accuracy?
A: 0-100% vol, ±5% vol (soil-specific calibration recommended for higher accuracy).
Q5: What is the temperature range?
A: -50~50°C, accuracy ±2°C.
Q6: What supply voltage does it require?
A: 5-28V DC.
Q7: Can it be used with iMaigg irrigation controllers?
A: Yes. MQ-S2 integrates with iMaigg controllers via RS485 Modbus-RTU.
Q8: What cable length is standard?
A: Standard cable is 5m. Custom cable length is available on request.
Q9: Does it need calibration?
A: Factory calibration is for loam soil. For other soil types, soil-specific calibration is recommended.
Q10: What is the default Modbus address and baud rate?
A: Address 01, baud rate 9600, data format 9600, N, 8, 1.
