A proximity sensor is a sensor used to detect the presence of nearby
objects in a non-contact nature. These sensors then convert the information
about presence or movement of an object into an electrical signal
Technical definition: Proximity Sensors
The essence of Proximity sensors is detecting the movement/presence of
objects without physical contact and converting that data into an electrical
signal. Therefore, all sensors that perform non-contact detection are
included in the category of proximity sensors. Proximity sensors are
also commonly referred to as “proximity switches” (by the Japanese
Industrial Standards), and include all the sensors that non-contact detect
objects within the general vicinity of the sensor.
The two main types of proximity sensors are Inductive and
Capacitive. The first ones use the eddy currents, generated in metallic objects
by electromagnetic induction, and the second ones detect changes in electrical
capacity in both metallic and non-metallic objects when approaching them with
There are other types of conventionally and commercially used proximity
sensors as well, that may use magnets, reed switches, ultrasonic, photoelectric
General Advantages and Features of Proximity Sensors
To further identify the specific added values of proximity sensors we ought
to recognize their features and advantages. An honest heads-up
is that the conventional users of these sensors chose them for their advantages
over the traditional optical or contact sensors.
This gives vast opportunities on its own, as extensive amounts of contact
sensors force compromised the design of the original applications –
no contact usually means no design changes.
Additionally, as proximity sensors need no contact to affect service life
(due to semiconductors usage) the general lifetime of these sensors is
Relatively high resistance in physical environments
Unlike optical detection methods, proximity sensors are usually not affected
by oily, dusty, or generally wet surroundings. On top of that, these sensors can
be used in temperatures ranging from –40 to 200 °C.
Unaffected by surface conditions
Proximity sensors are not compromised by colors or other surface
visuals conditions of the objects as main detected quantities are
within the physical changes of the subject.
Unlike contact-requiring switches, the proximity sensors offer
`higher speed detection.
Proximity Sensor: Types and their characteristics
Let’s go ahead and do a quick deep-dive into the most commonly known and
used proximity sensor types, to try and
understand the current trends this market offers to satisfy the demand of the
measurement needs. As it is known, the devil hides in plain sight: so with all
the advantages and added values we went through – it is fair to also point
out the potential downsides that the available proximity sensors will
Inductive proximity sensors are used to detect metallic objects such
as iron, copper, aluminum, brass, etc. These sensors essentially detect
the loss of magnetic properties due to eddy currents generated on a conductive
surface, by external magnetic fields.
These are composed of four main components: ferrite core with coils,
oscillator, Schmitt Trigger, and output switching circuit. The
operating principle is rather creative, yet not too complicated: first, an
alternative current travels to the coil, which generates an electromagnetic
field, so when a metallic object is close to the magnetic field – eddy current
builds up and inductive changes are reflected through coils.
The inductive proximity sensor creates a symmetrical oscillating
magnetic field even when a metallic object isn’t present, however, it
is only triggered when the target metallic object appears in the vicinity.
Inductive proximity sensors are widely used in applications where metallic
objects need to be detected, such as security-related
applications, or product counting, sorting applications especially for
automation purposes, however, these sensors have narrow limitations when it
comes to further applications.
These limitations (disadvantages) of inductive proximity sensors
are – detecting only metallic objects, the length of the detection
range, severe effects on performance by external objects such as other sensors,
extreme temperatures, chemicals and physically unstable harsh environments.
Unfortunately, these drawbacks are sufficient deal breakers for most
applications, whether considering the shielded or unshielded versions
of these sensors.
The next widely used type of proximity sensor is the capacitive type sensor:
these detect metallic and non-metallic objects alike (i. e. liquids, resins,
powders, etc.). Fundamentally capacitive sensors detect the
capacitance (the ratio of the amount of electric charge stored
on a conductor to a difference in electric potential) in between the sensing
object and the sensor.
An ordinary Capacitive Proximity Sensor is similar to a capacitor
with two parallel plates, where the capacity of the two plates is
detected. One of the plates is the object being measured (with an imaginary
ground), and the other is the Sensor's sensing surface (like inductive sensors,
these plates are linked to an oscillator, a Schmitt trigger, and an output
Due to the advantages over the inductive proximity sensors – the
capacitive sensors have a wider range of applications too:
moisture control, non-destructive sensing, as well as generally wide acceptance
within industrial applications, due to production automation, fluid
level/composition/pressure detection, etc.
These also have lawyer current consumption than the inductive type proximity
sensors and are resistant to the higher pressure of the physical environment,
however, being better than the inductive type, unfortunately, doesn’t remove
the limitations as such – the same drawbacks connected to law range of
sensing, and in addition, the above mentioned improvements come with a higher
price in comparison.
There are also higher range proximity sensors like Ultrasound, IR,
Photoelectric etc. To showcase some of their specific characteristics
let’s start with the IR Proximity Sensors.
IR Proximity Sensor
IR (infrared), is a sensor that emits a beam of infrared
light through which it detects the presence of an object. Infrared
proximity sensors consist of an infrared emitting LED and a light detector that
essentially detects the reflection (this happens through the signal processing
circuit that identifies the optical spot on PSD).
Working principle: Infrared light is emitted from the IR LED
emitter, The beam of light hits the object and gets reflected back into an
angle, the reflected light will reach the light detector, the sensor in the
light detector determines the position/distance of the reflective object.
Some common applications of IR proximity sensors are:
providing a count, when the objects cut the radiating light – it counts
security systems such as surveillance, burglar alarms, etc.,
monitoring and control applications.
It is surely advantageous to use these sensors, especially because of the
contactless detection, daytime and nighttime usability,
distance measurements of soft objects (unlike ultrasound proximity sensors), no
effects of corrosion or oxidation on the accuracy, and many more features. At
the same time, there are considerable disadvantages of these systems too, that
serve as dealbreakers for applications with diverse measurement demands.
The main disadvantages of IR proximity sensors:
affected by environmental conditions – inability to detect through
physical obstacles (doors, walls, dust, etc.);
requires clear visibility between transmitter and receiver to ensure
detection and communication;
performance is compromised over longer distances.
Ultrasonic proximity sensors
Another honorable mention is the ultrasonic proximity
sensors. These detect the presence of objects through the
emission of high-frequency ultrasonic ranges, which happens through
conversion of electric energy.
Working principle is following:
the sonic transducer emits sonic waves;
the waves then “bounce” off of the object;
the wave returns back to the sensor;
the distance or the proximity is identified as per the time it took to send
and receive the bounced sonic wave.
The most common applications are:
automation production processes;
fluid detection, etc.
Ultrasonic Proximity Sensors as well give opportunities of
contactless detection, without being affected by object color
and transparency, aren’t compromised by places with extreme conditions and
even detect in dark environments with low current consumption.
Disadvantages of Ultrasonic Proximity Sensors are vital red flags for
many use cases. These can be the Limited detection range (comes up
especially in comparison to inductive and capacitive sensors); Doesn’t work in
a vacuum (due to the sound waves, essential
for the detection); not able to measure the distance of objects with extreme
textures (as the sound waves are effected and too complicated to capture).
Future of Proximity Sensing: what is on the horizon?
The companies in need of proximity sensing, meaning a contactless system that
will easily provide reliable data – have gradually increased awareness of the
competitive advantage a better though through non-destructive system grants.
Unfortunately, in many cases, the companies have to combine multiple
of the above-mentioned systems, spend a round sum to engineer and set
up the combined system in the physical space as well as ensure communication
into the software, test the system, and develop additional maintenance
activities to ensure the quality of the engineered measurement system is always
For instance, a company that requires detection of a subject as well as
real-time precise data of temperature –
may need to choose IR and Capacitive Proximity sensors to ensure one of these
sensors “covers” for the drawbacks of the other. And even in this case –
should the environment be dusty – the temperature data will be
To be fair – we also need to take into account the costs coming
with the power consumption, setting up and maintenance of this
system – making it hard for the company to take the risk, and as a lot of
their competitors, they chose to proceed blindly, leaving the hope of reactive
This surely is nothing short of unsustainable ways of things, and the
Proximity Sensor market is a vital body that is more needed to react. This can
come in the form of R&D , AI, and through
sponsorship of EU, Governments, and unions of individual countries, as well as
international corporations – the proximity sensor market is to step
up and give this matter the deserved attention.
Our approach (contactless measurements)
We at RVmagnetics truly believe that science,
size, accuracy, and versatility matter. Fundamentally a Research &
Development company, we introduce to the market our own MicroWire sensors to provide Proximity
Sensing with one system that covers multiple measurements, as
well as overcomes the current Proximity Sensing flows, which have negatively
affected user decisions about data thus far.
Our system is custom developed based on the exact use case
our customers are challenged with. Based on the local physical environment, the
required resolution, sensitivity, physical quantities, and other KPIs defined by
the client – we aim to customize a Proof of Concept, a Prototype – and
finally launch the perfectly adjusted MicroWire sensor(s) with the sensing head,
and the customized software accordingly.
With our solutions – the clients can collect massive local data(due to the
sensing frequency of up to 10.000×/sec) which can be fed to software to enable
AI, Machine Learning, Predictive Maintenance, etc.
Surely our system is aimed for the specific demand looking to integrate an
economic advantage – a huge added value over their current available system,
and naturally, over the competition. With this in mind, however, it is important
to notice that MicroWire sensors are fairly inexpensive to
produce (from a gram of metallic alloy up to a kilometer of sensors),
and even with the electronics – the final price/unit of our sensor solutions
are largely competitive, to say the least.
This is why we believe that the urge to boost the proximity sensor market
with our – more versatile solution is an obvious benefit for the
market players, from consumer goods in international volumes all the
way to industrial “precision applications”.