Aquaterr M-350 Portable Soil Moisture Meter

Overview

The Aquaterr M-350 Portable Soil Moisture Meter is an engineered field instrument designed for rapid, in-situ quantification of volumetric water content (VWC) in soil and aqueous media using high-frequency capacitance sensing technology. Operating at 50 MHz, the M-350 measures dielectric permittivity changes induced by water molecules within the soil matrix—enabling direct correlation to VWC without calibration against gravimetric standards under standard soil textures (sandy loam to clay loam). Its probe employs a coaxial electrode configuration embedded in aerospace-grade stainless steel, ensuring mechanical durability during repeated insertion into compacted or rocky soils while maintaining signal integrity across heterogeneous profiles. Unlike time-domain reflectometry (TDR) or neutron probe systems, the M-350 delivers immediate readings with no warm-up delay, zero external power requirements beyond its internal 9V battery, and no need for laboratory validation—making it suitable for routine monitoring in precision agriculture, turfgrass management, ecological restoration, and irrigation scheduling.

Key Features

• High-stability 50 MHz capacitance sensor with temperature-compensated electronics for consistent VWC output across ambient ranges from −10 °C to +50 °C
• 76.2 cm rigid probe optimized for profiling root zones (0–60 cm depth) in agricultural fields, golf course fairways, and urban green spaces
• Real-time digital display with automatic hold function and unit toggle (VWC %, m³/m³)
• Ruggedized housing and corrosion-resistant stainless-steel probe rated for repeated use in saline, acidic, or alkaline soils
• Battery-powered operation (9V alkaline) supporting ≥1,000 measurement cycles per charge; low-battery indicator alerts prior to voltage drop affecting sensor linearity
• Calibration traceable to NIST-traceable reference soils; factory calibration certificate provided with each unit

Sample Compatibility & Compliance

The M-350 is validated for direct insertion into mineral soils (sand, silt, clay, and their mixtures), organic substrates (peat, compost, potting mixes), and liquid-phase samples including irrigation water, leachate, and nutrient solutions. It is not intended for frozen, highly conductive (>8 dS/m EC), or gravel-rich matrices (>30% stone fraction) where sensor-field coupling degrades. The instrument complies with ASTM D5530–22 (“Standard Test Method for Determining Volumetric Water Content of Soil Using Capacitance Probes”) and supports data integrity practices aligned with ISO/IEC 17025:2017 clause 7.7 (result reporting) and FDA 21 CFR Part 11 when paired with optional Aquaterr LogLink software (audit trail enabled). No hazardous materials are used in construction; RoHS 3 and REACH compliance verified.

Software & Data Management

While the M-350 operates as a standalone handheld meter, it integrates seamlessly with Aquaterr’s LogLink Desktop Suite (v4.2+), enabling CSV export, spatial mapping via GPS-tagged metadata, and statistical trend analysis across time-series datasets. The software enforces user-defined QA/QC flags (e.g., outlier rejection, depth-weighted averaging), generates PDF reports compliant with GLP documentation standards, and maintains full audit trails—including operator ID, timestamp, location coordinates, and calibration history—for regulatory review. All data files are encrypted at rest (AES-256) and support secure transfer via TLS 1.3.

Applications

• Precision irrigation management: Quantifying real-time moisture deficits to optimize drip or pivot scheduling and reduce water waste
• Turfgrass health assessment: Monitoring root-zone hydration in golf greens, sports fields, and municipal parks to prevent drought stress or overwatering
• Salinity impact studies: Supporting concurrent interpretation with EC-350 units to correlate VWC shifts with electrical conductivity trends in sodic soils
• Soil hydrology research: Validating infiltration models and evapotranspiration estimates in field-scale lysimeters and watershed monitoring networks
• Environmental remediation: Tracking moisture dynamics during phytoremediation or bioventing operations where water content governs microbial activity

FAQ

Does the M-350 require soil-specific calibration?
Field calibration is recommended for soils outside the standard textural range (e.g., volcanic ash, pure sand >95%, or peat >80% organic matter); Aquaterr provides application-specific calibration kits and protocols.
Can the probe be inserted into saturated or flooded soil?
Yes—the stainless-steel housing and sealed electronics permit temporary submersion; however, prolonged exposure above 100% VWC may trigger saturation warnings and requires post-use drying before storage.
How does temperature affect measurement accuracy?
Internal temperature compensation corrects for thermal drift between −10 °C and +50 °C; measurements outside this range require manual correction using published dielectric temperature coefficients.
Is the M-350 compatible with GIS platforms?
Yes—LogLink exports geotagged .CSV and .KML files directly importable into ArcGIS Pro, QGIS, and Farm Management Information Systems (FMIS) such as Granular or Climate FieldView.
What maintenance is required to ensure long-term accuracy?
Annual verification against certified reference soils is advised; probe cleaning with isopropyl alcohol after each use prevents biofilm accumulation and ensures repeatable electrode contact resistance.