Because you cannot see or smell Electromagnetic fields and radiation, and only a few people at present can feel them, it is difficult to envisage what you need to measure.
Measuring the Electromagnetic fields and radiation is important, since the key to limiting your Electrosensitivity is avoiding or reducing your exposure.
There are three main values which are measured and relate to what you may feel if you are sensitive to Electromagnetic fields and radiation,
1. Magnetic fields
These are Extremely Low Frequency (ELF), typically of 50-60 Hz and found near power-lines and supply cables.
They are measured in nanoTesla (nT).
If you are sensitive to magnetic fields, a ramp or gradient of 7 nT at, say, 30 nT (a typical house), may trigger a symptom.
Values above 200 nT are linked with leukemia and other cancers.
Brain waves are often under 10 or 40 Hz.
It is almost impossible to shield against these magnetic fields.
2. Radio waves
VHF and FM radio at about 100 MHz is counted as radio waves.
3. Microwaves, also called radio frequency
Cellphones and WiFi use microwaves, such as 880 MHz or 2.45 GHz. They are measured in either:
(a) Electric fields, peak to peak for biological effects on cell membranes, in Volts/meter. ES people can feel effects at under 0.02 V/m.
(b) power density, as in microWatts/meter squared. The BioInitiative Report of 2012 recommends a maximum of 6 for the healthy general public and 3 for children, the elderly and sensitive people.
In addition there is the SAR (Specific Absorption Rate) used for cellphones. This was designed for measuring a change of 1 degree of heat over an average of 6 minutes. It is therefore not suited to Electrosensitivity which is caused by biological reactions because of long-term and/or low-level exposure.
For biological effects, it is essential to measure:
(a) peak levels, not the average as used for the invalidated heating hypothesis,
(b) cumulative exposure, not the 6 minute exposure used by the invalidated heating hypothesis.
For 'dirty electricity' or voltage transients on wiring and cables, a special meter is required.