Overview
ISO 18386:2025 defines a screening method for soil temperature measurement using an infrared (IR) thermometer. The standard positions IR detection as a quick, non-contact approach for soil temperature that complements more accurate conventional methods. It is intended for use across geology, geotechnics, biology, agricultural sciences, climate studies and metrological investigation, and is recognized within ISO 4974 as a quick measurement and as a screening method per ISO 12404:2021.
Key Topics
- Principle: IR thermometers estimate temperature from thermal (black‑body) radiation emitted by soil. A lens focuses IR radiation onto a detector, producing an electrical signal that is converted to temperature after ambient compensation.
- Advantages: Rapid, remote (non‑contact) readings; useful where probe placement is difficult or where speed and hygiene are priorities.
- Limitations: Readings can be affected by emissivity assumptions, IR attenuation, and reflected radiation from nearby hotter bodies; accuracy may be lower than contact thermometers.
- Apparatus (examples from the standard):
- Casing pipe with inner rod (commonly outer pipe i.d. 31 mm and inner rod o.d. 30 mm) to protect hole walls.
- Shock‑absorbing (low‑rebound) hammer or wooden head maul for inserting casing.
- Auger when hammer insertion is impractical.
- IR sensor/thermometer (typical working range noted in the standard: about –10 °C to 80 °C).
- Procedure highlights:
- Drill a protected hole using a casing pipe; remove inner rod to reveal the hole while leaving outer pipe in place.
- Apply IR detection either close to a target spot in the hole or from the top with appropriate focusing optics.
- Follow manufacturer guidance on emissivity settings and ambient compensation.
- Quality assurance: The document includes requirements for QA/QC and reporting to ensure consistent screening results.
Applications
ISO 18386:2025 is practical for field‑based, time‑efficient soil temperature surveys and screening campaigns where rapid spatial coverage is needed. Typical use cases:
- Quick assessment of soil temperature for agronomy (crop germination and growth context).
- Preliminary surveys in geology and geotechnics where many spots must be screened rapidly.
- Supporting climate change and greenhouse gas flux studies by providing temperature context for microbial activity estimations.
- Metrological investigations and situations where contact probes are impractical.
Benefits include reduced measurement time per spot, safer non‑contact operation, and easier logistics for large surveys. Users should weigh speed against the lower precision compared with contact thermometry.
Related Standards
- ISO 4974 - Guidance on measurement approaches for soil temperature (discusses quick vs conventional methods).
- ISO 12404:2021 - Definitions and guidance for screening methods.
- Relevant ISO/TC 190 publications and national guidance for soil quality and temperature measurement.
For implementation, consult the full ISO 18386:2025 text for procedural details, QA/QC requirements and test report templates.