Principles Of Operation - Loma IQ2 User Manual

28
Using the metal
detector

Principles of operation

Before using the metal detector it is helpful to understand its principle of operation, as this
will help you understand the measurements it makes and the basis it uses for detecting a
metal contaminant in a foodstuff.
Although several different types of metal detector are produced, to suit different types of
foodstuff, they all operate in essentially the same way.
The product passes through a tube around which are three coils, as shown in the following
diagram:
r
e i v e
R e c
The central coil is referred to as the transmitter coil, and this transmits a radio-frequency
signal similar to the frequencies used in AM broadcasting. Spaced equally on each side of
the transmitter coil are two receiver coils, which act as aerials to pick up the radio signal. The
metal detector measures the difference in voltage between these coils, and this is referred to
as the signal.
t t e r
s m i
T r a n
r
e i v e
R e c
Oscillator
Product
7031