Group 7 Assignment 1: Instrumentation and Control (Evening class)
Okello Patrick Luke
18/U/EMD/21451/PD
Mulindwa B. Trevor D.
18/U/EME/9658/PE
Mawanda Jonathan
18/U/EME/17720/PE
BAKISULA STEPHEN
18/U/EMD/21449/PD
ALINDE WILLIAM
18/U/EME/17722/PE
NKAHIKA RUHINDI
18/U/EMD/17776/PD
KIRUMIRA DENIS
18/U/EME/17718/PE
MUBIIRU ISAAC Wellington
18/U/EME/21444/PE
Oluka Job
18/U/EME/21443/PE
NAMARA ISAAC
18/EMD/17778/PD
Twinomugisha Clever
19/U/EMD/17678/PD
TOPIC: INDUCTIVE PROXIMITY SENSERS
Inductive proximity sensor:
An inductive sensor is a non-contact type of sensor, helpful in the detection of
metallic objects. It can sense ferrous as well as non-ferrous materials. The sensing
range is up to 100 mm. However, the level of sensitivity defers while sensing nonferrous material.
MODE OF OPERATION
The oscillator creates a symmetrical, oscillating magnetic field that radiates from the
ferrite core and coil array at the sensing face. When a ferrous target enters this
magnetic field, small independent electrical currents (eddy currents) which
are induced on the metal’s surface.
An inductive proximity sensor has the frequency range from 10 to 20 Hz in ac, or 500
Hz to 5 kHz in dc. Because of magnetic field limitations, inductive sensors have a
relatively narrow sensing range like from fractions of millimetres to 60 mm on an
average.
Due to this, load will be caused on the sensor that decreases the electromagnetic
field amplitude. If the metal object moves towards the proximity sensor, the eddy
current will increase accordingly. Thus, the load on the oscillator will increase, which
decreases the field amplitude.
The Schmitt trigger block monitors the amplitude of the oscillator and at particular
level (predetermined level) the trigger circuit switches on or off the sensor. If the
metal object or target is moved away from the proximity sensor, then the amplitude
of the oscillator will increase.
The above image shows the waveform of the inductive proximity sensor oscillator in
the presence of the target and in the absence of the target.
Nowadays, inductive proximity sensors are available with different operating
voltages. These inductive proximity sensors are available in AC, DC, and AC/DC
modes (universal modes). The operating range of the proximity sensor circuits is
from 10V to 320V DC and 20V to 265V AC
CONSTRUCTION
The sensing face can be of PEEK(Poly-ether-ether-ketone), Ceramics, etc.
depending on the application requirement. The selection of housing material is
based upon the environment where it is going to be exposed. Some of the materials
are; Stainless Steel V2A, Nickel-plated or Teflon-coated brass, PBTB (polybutylene
terephthalate), PPS (Polyphenylene Sulfide), PA (Polyamide)
•
High-grade stainless steel is the best option for hygienic areas. It can comply
with food-grade standards.
•
The PBTB material is resistant to abrasion, heat and cold, etc.
•
The PPS material can withstand higher temperatures. The material can
withstand 200 °C temperature.
The electronic circuit is resin-potted in a vacuum.
The cable material options are –
•
PVC (Polyvinyl Chloride): Medium resistant to oil, grease, and highly resistant
to abrasion.
•
PUR (Polyurethane rigid foam): Gives high resistance to oil, grease. It is nonbrittle and highly resistant to abrasion.
•
Silicon: This material can withstand high temperatures (-50 °C to + 180 °C)
but is medium resistant to oil and grease.
APPLICATION
•
Can be used to monitor the rotational speed of the machine.
•
In conveyor application, you can use it to monitor the position.
•
In a pipe manufacturing plant, the sensors are best for metal pipe detection
for further processing of pipe.
•
Robotic arm control is possible with the help of inductive sensors.
•
You can use an Inductive proximity sensor to count the metal cans.