# Logging EMF instrument

> Any of the above with unattended recording: required whenever the assessment depends on an average, a night-time value or a 95th percentile rather than a spot reading.

- Canonical URL: https://emfbase.com/meters/data-logger
- Collection: Instruments
- Record id: `meters:data-logger`
- Status: verified
- Last verified: 2026-08-12
- JSON: https://emfbase.com/api/meters/data-logger
- Also known as: EMF logger, 24 hour logging meter

## Key values

- **Band covered:** instrument dependent
- **Quantities measured:** magnetic flux density, power density, electric field strength
- **Typical price:** $200–$3000

## Detects

- Diurnal variation in power-line loading
- Night-time smart-meter and mesh traffic
- Intermittent sources that a spot survey misses entirely

## Cannot detect

- Anything outside the host instrument's band

## What to insist on

- Sample interval fast enough for pulsed sources, with peak capture per interval
- Exportable raw data, not just a summary screenshot
- Battery life covering the full logging window

## Related records

- [ELF magnetic field survey](https://emfbase.com/protocols/elf-magnetic-survey): A source-finding walkthrough plus a 24-hour log, because power-frequency magnetic fields track electrical load and a spot reading answers almost nothing.
- [High-voltage transmission line](https://emfbase.com/emitters/high-voltage-transmission-line): Fields directly beneath a loaded transmission line reach tens of milligauss and fall off roughly with distance for a balanced three-phase circuit, reaching background at 30–60 m for typical loadings.

## Sources

- `sbm-2024` Institut für Baubiologie + Nachhaltigkeit (IBN) (2024). *Building Biology Evaluation Guidelines for Sleeping Areas (SBM-2024)*. https://buildingbiology.com/site/downloads/SBM-2024_EVALUATION_GUIDELINES_EN.pdf — ngo, link checked 2026-08-12

Data licence: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Dataset version 2026.08.1. Retrieved from EMFBase, https://emfbase.com.

This record is reference data, not medical or legal advice. Regulatory limits, scientific guidelines and precautionary values are labelled separately and answer different questions.