Instruments

Measurement of electric and magnetic fields
This is a summary of instruments for measuring fields. A more detailed technical description of the issues is also available.

The first commercial instruments designed specifically for measuring power-frequency fields became available in the 1980s. There are now many instruments available, which vary in the number of axes they measure, how sophisticated the electronics are, whether they record fields, and whether they are meant for survey use or as a personal monitor. More on how instruments differ

There is no “correct” or “best” meter. The best meter to use depends on the purpose it is to be used for.

Measuring magnetic fields
There are three different sensors widely used for measuring magnetic fields: Search coils, fluxgate magnetometers, and Hall-effect devices.

Most practical instruments for power frequencies use search coils, either a single coil or three orthogonal coils. The coils themselves can either be made as small as possible, for use in personal exposure meters where size and weight are important criteria, or they can be larger, often 0.1 m across, to increase sensitivity and provide some spatial averaging. More on different sensors

Measuring electric fields
Meters for electric fields usually use as sensors two parallel conducting plates. Alternative sensors, eg based on rotation of polarised light, are less common.

Three-axis electric-field meters are available, but single-axis meters are more common.

A person holding an electric-field meter would perturb the field. To measure the unperturbed field, the meter is usually held at the end of a long non-conductive horizontal rod or a vertical tripod. This can reduce perturbation to acceptable levels, but care is still needed to get accurate readings. More on how to do accurate readings

Personal exposure meters do exist for electric fields. However, wearing a meter on the body perturbs the electric field being measured in unpredictable ways.

Manufacturers of instruments
We do not recommend any particular instruments or manufacturers, however, you may like to look at the following web sites:

Enertech Consultants: http://www.enertech.net/
Perspective Scientific: http://www.perspective.co.uk/
Holaday Industries: http://www.emctest.com/Holaday/Default.htm
Wandel and Goltermann (now Acterna) http://www.acterna.com/united_kingdom/index.html

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