It depends on the machine design and the original equipment manufacturer.
Most metal detectors for use on a conveyor belt provide a "normally open" and a "normally closed" set of relay contacts so that the customer can choose the operating mode best suited for "fail-safe" operation.
The customer (or applications technicain) provides the interlocking permissive voltage from the machine controls to the detector for interrogation and logical use.
It is possible to use a 4 -20mA signal but not feasible unless the customer is wanting to monitor quantity of metal and not just the existance of metal in a process.
How does the metal detectors work? The
operation of metal detectors is based on the principles of electromagnetic
induction. It generates a rapidly changing magnetic
field by running the alternating current though coil,
which will generate eddy currents inside the metal objects. Thereby, the eddy
currents will create a new magnetic field that affects the original one, and
then the metal detectors will utter a high-pitched tone. The accuracy and
reliability of the metal detectors depend on the stability of frequency of
electromagnetic launchers. Generally, the frequency is between 80
to 800 KHz. The lower the frequency, the better detection for iron objects. Similarly,
the higher the frequency, the better detection for high carbon steel objects. The
sensitivity of the metal detectors decreases with the expanding detecting
range. Moreover, the induction signal depends on the metal particle
size and conductivity. quoted from detectorall
Metal Detector Output Signal
Re: Metal Detector Output Signal
