EMFields AM-11, User Manual

Page: 17 / 28

17
Why are there two different readings?
We display two different types of reading, as they
each represent different but important aspects of
your exposure: Peak Signal Strength and Power Flux
Density (PFD).
Peak Signal Strength is the electric field strength,
measured in volts per metre (
V/m). These readings
are on the left column of LEDs and the top line of the
OLED display.
Power Flux Density (PFD) is the time-averaged
power in microwatts per square metre ( µW/m 2 ).
These readings are on the right column of LEDs, and
the bottom line of the OLED display.
The traditional scientific viewpoint is that the only
relevant measurement of high-frequency RF fields is
the total amount of absorbed energy from exposure,
which causes body tissue heating, measured as PFD.
This is the basis of most official international
guidelines, and so most legal guidelines and limits
are specified as a time-averaged PFD limit.
However, there is now a large body of high-quality
scientific and medical evidence demonstrating
biological effects from exposure levels far below
these standards, and the evidence is strongly
suggestive that most of the adverse effects are not
related to the total absorbed energy as they occur
far below levels of measurable tissue heating.