Measuring EMFs

It is quite easy to measure magnetic fields.  Instruments are usually based on search coils (though other types exist as well) and can be small and handheld, or larger and more sophisticated.  Measuring electric fields is possible too but harder because the person making the measurement often perturbs the field.

We have provided two pages about EMF instruments.

Specific instruments

We do not endorse any specific manufacturer.  But we privide some links to various manufacturers and instruments.

Calculating EMFs

If you know that there is one dominant source of EMFs present it is often possible to calculate the fields it produces.  Overhead lines and underground cables lend themselves to this.  It is possible for substations too, but harder because the geometry is more complicated.  You can't easily do calculations for low-voltage distribution sources because you don't normally know the currents accurately enough.

Calculations are often preferable to measurements because you can perform them for any desired conditions rather than being limited to the particular conditions at the time you do the measurement.

Calculations can be as accurate as you like.  You can see a comparison of calculations and measurements from an overhead line and here for a discussion of how accurate the calculations can be. 

Calculations (and measurements) are often performed at 1 m above ground because this is the relevant height for assessing the induced current in a person - see a full explanation.