ADCON SM1 Multi-Depth Soil Moisture and Temperature Profiling Sensor

Overview

The ADCON SM1 is a multi-depth, integrated soil moisture and temperature profiling sensor engineered for long-term, high-reliability environmental monitoring in agricultural, hydrological, geotechnical, and ecological research applications. It employs capacitive dielectric sensing technology to measure volumetric water content (VWC) across discrete soil layers, while simultaneously capturing in-situ soil temperature profiles using precision thermistors. Unlike single-point sensors, the SM1 provides vertically resolved data—critical for understanding infiltration dynamics, root-zone water availability, evapotranspiration modeling, and vadose zone characterization. Its modular tube design enables customizable deployment depths (30–150 cm), with moisture sensors spaced every 10 cm and up to five temperature sensors positioned at 15, 45, 75, 105, and 135 cm—optimized to capture thermal gradients across key soil horizons. The sensor operates within the widely adopted SDI-12 digital interface standard, ensuring compatibility with most industry-standard dataloggers (e.g., Campbell Scientific CR series, Onset HOBO, Delta-T Devices DL2/3), and supports low-power, multi-sensor networks ideal for remote or solar-powered field stations.

Key Features

• Capacitive-based volumetric soil moisture measurement with ±2% accuracy across 0–100% VWC range and 0.1% resolution—calibrated for mineral soils and validated per ASTM D5859 and ISO 11274 protocols.
• Integrated high-stability thermistor array with ±0.5 °C accuracy (0–70 °C) and 0.125 °C resolution—traceable to NIST-certified reference standards.
• Rugged, IP67-rated housing constructed from UV-stabilized, shrink-resistant PVC; aluminum and polymer mounting bracket included for stable vertical alignment during slurry or conduit installation.
• Modular length configuration: five standard options (30, 60, 90, 120, 150 cm) allow precise adaptation to site-specific soil profile requirements without over-engineering.
• SDI-12 compliant interface with robust 7-pin Pentax waterproof connector and 5 m shielded cable—enabling daisy-chaining of up to 62 sensors on a single bus line per SDI-12 specification.
• Low-voltage operation (5.6–12 VDC) and sleep-mode current draw <100 µA—designed for extended battery life in unattended deployments exceeding 12 months.

Sample Compatibility & Compliance

The SM1 is validated for use in mineral soils, loams, sandy clays, and volcanic ash substrates. It is not recommended for highly saline (>8 dS/m EC) or organic-rich peat soils without site-specific calibration due to dielectric constant interference. All electrical components comply with IEC 61326-1 (EMC for measurement equipment) and RoHS 2011/65/EU directives. The sensor housing meets ISO 22868:2020 requirements for long-term burial integrity under cyclic wet-dry and freeze-thaw conditions. Data acquisition workflows support GLP-compliant metadata tagging—including sensor ID, depth assignment, timestamp, and diagnostic flags—for traceability in regulatory reporting (e.g., USDA NRCS SNTL, USGS Climate Response Networks).

Software & Data Management

Raw SDI-12 output is parsed natively by ADCON’s ADELIE™ data management platform and third-party tools including LoggerNet (Campbell), HOBOware Pro (Onset), and EnviroPro (Delta-T). Each measurement packet includes embedded depth identifiers, enabling automated layer-mapped time-series generation. ADELIE supports automated QA/QC flagging for out-of-range values, sensor drift detection (via baseline stability monitoring over 30-day windows), and export to CF-netCDF or EPA WQX-compliant formats. Audit trails meet FDA 21 CFR Part 11 requirements when deployed with certified datalogger firmware (v3.2+), including electronic signatures, immutable timestamps, and change history logs.

Applications

• Irrigation scheduling and deficit irrigation optimization in precision agriculture—enabling real-time root-zone water status assessment for drip and subsurface drip systems.
• Landfill cover performance monitoring per EPA SW-846 Method 9095B, tracking moisture migration through composite liner systems.
• Vadose zone flux modeling in hydrogeological studies—supporting HYDRUS-1D and STOMP numerical simulations with high-vertical-resolution boundary condition inputs.
• Permafrost active-layer monitoring in Arctic and alpine environments—leveraging extended low-temperature capability (–55 °C) and freeze-thaw cycle resilience.
• Ecological restoration projects—validating soil moisture thresholds for native seed germination and mycorrhizal colonization across successional stages.

FAQ

What is the maximum number of SM1 sensors that can be connected to a single SDI-12 bus?

Up to 62 sensors may be addressed on one SDI-12 bus, provided each unit has a unique address and total cable length remains ≤ 610 m (2000 ft) with appropriate shielding and termination.
Can the SM1 be calibrated for organic or saline soils?

Yes—ADCON provides application-specific calibration services using Topp’s equation modifications and dielectric mixing models (e.g., Roth et al., 1992); users must supply representative soil samples for lab validation.
Is the 5 m cable field-replaceable?

Yes—the 7-pin Pentax connector is standardized; replacement cables (part #CBL-SM1-XXm) are available in lengths from 1 m to 100 m, all pre-terminated and tested to IP68.
How does the SM1 handle freezing conditions?

The sensor remains operational down to –55 °C; however, volumetric water content readings below 0 °C reflect unfrozen water content only and require interpretation using soil-specific freezing point depression models.
Does the SM1 support wireless telemetry integration?

Yes—it interfaces seamlessly with ADCON’s GPRS/LTE-based TELEMAC™ gateways and LoRaWAN edge nodes (e.g., TELEMAC-LR), enabling cloud-uploaded time-series with configurable sampling intervals (1 min to 24 h).