# Body-voltage measurement

> The building-biology method for grading a sleeping area's AC electric field: a high-impedance millivoltmeter, a hand electrode, and a documented ground reference.

- Canonical URL: https://emfbase.com/protocols/body-voltage-survey
- Collection: Measurement protocols
- Record id: `protocols:body-voltage-survey`
- Status: verified
- Last verified: 2026-08-12
- JSON: https://emfbase.com/api/protocols/body-voltage-survey
- Also known as: how to measure body voltage

## Key values

- **Quantity measured:** body voltage

## Goal

Quantify capacitive coupling from building wiring to a person at the sleeping position, and identify which circuits and devices contribute.

## Equipment

- Body-voltage measurement kit
- AC electric field meter

## Procedure

1. Establish and document the ground reference: protective earth at a socket, or a dedicated ground rod. Readings are not comparable across different references.
2. Lie or sit in the normal sleeping position, holding the hand electrode, with the meter on AC millivolts.
3. Record the baseline with the room in its normal night-time state.
4. Unplug items one at a time — bedside lamp, charger, extension lead — recording the reading after each.
5. Switch off individual circuits at the consumer unit, recording after each, to attribute the remainder to specific circuits.
6. Repeat after any mitigation (demand switch, shielded cable, shielding paint) using the identical reference and posture.
7. Report the ground reference, posture and circuit states alongside every number.

## Pitfalls

- Comparing a reading against someone else's number when the ground reference differs
- Assuming a low body voltage means low magnetic field exposure — the two are independent
- Grounding a shielding surface incorrectly and creating a larger field than before
- Working inside a consumer unit without a qualified electrician

## Interpret results against

- Building Biology SBM-2024 AC electric field bands

## Related records

- [Bedroom wiring AC electric field](https://emfbase.com/emitters/bedroom-wiring-electric-field): Live conductors in walls and in lamp flex create a power-frequency electric field that couples to the body whether or not any current flows; building biology grades below 1 V/m with ground reference as 'no anomaly'.
- [Demand switch (Netzfreischalter)](https://emfbase.com/shielding/demand-switch): A relay in the consumer unit that de-energises a circuit when no load is drawing current and re-energises it when a switch is thrown, eliminating the bedroom AC electric field overnight.

## 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.