Different applications require different types of proximity sensors, with each sensor being designed to serve a specific purpose. Other factors, such as target type and operating range or response time, also dictate the type of sensor to use. With that in mind, the information in this article will help you find the proximity sensor types that will work best for your project.
About Proximity Sensor
The proximity sensor refers to a type of contactless sensor that emits a field of energy to detect the presence—or absence—of object. This can be a proximity sensor for mobile, proximity sensor for security systems, or the different types of proximity sensors used in industrial automation.
Because of their non-contact nature, proximity sensors have many advantages over contact sensors. They are reliable, durable and require low maintenance. They also do not produce any physical movement or heat transfer to the target object, and can be used in harsh environments.
A proximity sensor may use electromagnetic waves, light, or ultrasound to detect object. Some only detect metals, while others can pick both metal and non-metal targets.
Still, some types of proximity sensors offer longer detection ranges than others, and so on. The proximity sensor and its types in today’s world are discussed in the next section.
Types of Proximity Sensors
Based on the different forms of detection technologies, proximity sensors are classified into five categories: Inductive Proximity Sensor; Capacitive Proximity Sensor; Ultrasonic Proximity Sensor; Magnetic Proximity Sensor; and Optical Proximity Sensor. Learn about these types of proximity sensors, including their different uses, below.
1. Inductive Proximity Sensor
The inductive proximity sensor is called so for using inductance principles to detect the presence of a metal target, without making any physical contact. One of the most common types of this sensor is the eddy current proximity sensor.
These sensors primarily consist of an oscillator, a coil around a ferrite core, and a Schmitt trigger. Here’s now see how an inductive proximity sensor works:
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- During operation, the oscillator generates an alternating current that produces an alternating electromagnetic field around the coil.
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- This field radiates from the coil to form the detection zone.
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- If a metallic object enters this detection zone, the oscillating magnetic field induces electric currents in its body. These are called eddy currents.
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- The eddy currents then start producing an alternating magnetic field, interfering with the original oscillating field from the sensor and changing its properties.
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- This change activates the Schmitt trigger and the sensor is able to detect.
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- Note that these types of proximity sensors cannot detect non-metallic objects as such materials will not produce Eddy currents.
Application: One of the benefits of inductive sensors is their ability to operate in contaminated environments: they’re resistant to the presence of oil, dirt, and even moisture. Inductive proximity sensors are, therefore, widely used in industrial, automotive, and machine tool applications.
GEYA Proximity Sensor technical parameters：
| Order No：GYBT2-M8-NA/GYBT2-M8-NB/GYBT2-M8-PA/GYBT2-M8-PB/GYBT2-M8-DA/GYBT2-M8-DB | |
| Technical parameters | |
| General instructions | |
| Output type | NPN NO、NPN NC、PNP NO、PNP NC、DC NO、DC NC |
| Installation method | Flush mounting |
| Rated operating distance Sn | 2mm |
| Raliable operating range distance Sa | 0..1.6mm |
| Standard detection target | 8*8*1t(Q253A) |
| Rated grade | |
| Rated voltage UB | 10…30VDC |
| Switch frequency f | 1.5KHz |
| Hysteresis range | 1-15%of detection distance |
| Repeatability | <3%of detection distance |
| No-load current lo | <15mA |
| Leakage current Ir | <100uA |
| Voltage drop Ud | DC three-wire<2V,DC two-wire<3V |
| Working current IL | <100mA |
| Circuit protection | Reverse polarity protection,output short circuit protection,surge absorption |
| Switch status indication | Red LED indicator |
| Surroundings | |
| Ambient temperature | -25℃…70℃(248.…358K) |
| Temperature effect | -25℃…70℃,detection distance within 10%at +24℃ |
| Environment humidity | 35…95%RH |
| Voltage influence | <3% |
| Mechanical characteristics | |
| Wiring form | Standard wire length 2m |
| Case materia | Brass nickel plating |
| Inductive surface | PBT |
| Protection leve | IP66 |
| High voltage resistance | 1000VAC,50/60Hz for 1 minute between charged parts and the case |
| Insulation resistance | 50MΩ or more(DC500V)for the charged parts and case |
| Vibration resistance | 10～55 Hz,amplitude 1.5mm X,Y,Z each direction 2H |
| Certifications and Standards | |
| Product cetificates | |
| Standards compliant | EC/EN 60947-5-2:2004 |
Capacitive proximity sensor
2. Capacitive Proximity Sensor
The capacitive proximity sensor uses an electric field to detect the presence of a target object. It’s basically an open capacitor whose other plate is replaced by the target, while the air between the sensor plate and target forms the dielectric. Here is how a capacitive proximity sensor works:
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- When the target enters the sensor’s range, it forms a capacitance with its sensing plate, which increases as the object draws nearer.
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- This action changes the capacitance value of the circuit, which in turn produces an electrical signal used to detect presence.
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- The capacitive sensor can detect both metals and nonmetals. These can be powders, granules and liquids or even solid objects.
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- Because the working principle of capacitive proximity sensor is based on the gradual increase of the capacitance, its sensing speed is generally lower than that of inductive sensors.
Application: Capacitive proximity sensors are used in a wide range of applications, including food and beverage production processes, level detection, material handling, automation control systems and other industrial environments. In the world of electronics, this is the type of proximity sensor for mobile phone or tablet sensing applications.
| Order No：GYBT2-M8-NAH/GYBT2-M8-NBH/GYBT2-M8-PAH/GYBT2-M8-PBH/GYBT2-M8-DAH/GYBT2-M8-DBH | |
| Technical parameters | |
| General instructions | |
| Output type | NPN NO、NPN NC、PNP NO、PNP NC、DC NO、DC NC |
| Installation method | Flush mounting |
| Rated operating distance Sn | 2mm |
| Raliable operating range distance Sa | 0..1.6mm |
| Standard detection target | 8*8*1t(Q253A) |
| Rated grade | |
| Rated voltage UB | 10…30VDC |
| Switch frequency f | 1.5KHz |
| Hysteresis range | 1-15%of detection distance |
| Repeatability | <3%of detection distance |
| No-load current lo | <15mA |
| Leakage current Ir | <100uA |
| Voltage drop Ud | DC three-wire<2V,DC two-wire<3V |
| Working current IL | <100mA |
| Circuit protection | Reverse polarity protection,output short circuit protection,surge absorption |
| Switch status indication | Red LED indicator |
| Surroundings | |
| Ambient temperature | -25℃…70℃(248.…358K) |
| Temperature effect | -25℃…70℃,detection distance within 10%at +24℃ |
| Environment humidity | 35…95%RH |
| Voltage influence | <3% |
| Mechanical characteristics | |
| Wiring form | Connector |
| Case materia | Brass nickel plating |
| Inductive surface | PBT |
| Protection leve | IP66 |
| High voltage resistance | 1000VAC,50/60Hz for 1 minute between charged parts and the case |
| Insulation resistance | 50MΩ or more(DC500V)for the charged parts and case |
| Vibration resistance | 10～55 Hz,amplitude 1.5mm X,Y,Z each direction 2H |
| Certifications and Standards | |
| Product cetificates | |
| Standards compliant | EC/EN 60947-5-2:2004 |
Ultrasonic proximity sensor
3. Ultrasonic Proximity Sensor
The ultrasonic sensor is somewhat different from inductive and capacitive sensors. These types of proximity sensors work by emitting ultrasonic waves—or sound waves with a frequency higher than the upper limit of human hearing, which is around 20 kHz. The working of ultrasonic proximity sensor is described below:
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- The ultrasonic sensor consists of these parts: transmitter, receiver, signal processor, amplifier and power supply module, and works by sending out high-frequency sound pulses.
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- When the sound waves encounter an obstacle, they will bounce back to the receiver.
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- The receiver then uses this information to determine the presence as well as distance between the object and the sensor.
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- Ultrasonic proximity sensors offer fast detection speed, even for small objects, and have a wide sensing range. They can also detect both solid and liquid targets in their sensing zone.
Application: Ultrasonic proximity sensors are mainly used in robotics, obstacle detection and avoidance systems, industrial automation, parking sensors, etc. In addition, these types of sensors can also pick up vibrations, making them suitable for vibration monitoring applications.
Optical proximity sensor
4. Optical Proximity Sensor
The optical proximity sensor works on the principle of light reflection. The light is either the visible or infrared spectrum. The sensor emits light towards a target object and measures the amount of reflected light back to it.
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- In most cases, the optical proximity sensors are used in conjunction with an infrared LED or laser diode. When a target object is near enough to the sensor, it reflects some of the light energy back to the detector.
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- This will then be amplified and used as an electrical signal to detect the presence of the object.
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- The optical proximity sensors are usually not affected by dust, dirt or moisture.
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- They also have a high resolution and can detect even very small objects in their sensing range with ease.
Application: Optical proximity sensors are widely used for level detection in liquids, position sensing in machines and automation processes. They are also used as metal detectors in security systems and access control devices. These types of proximity sensors have also found application in navigation systems for cars or drones.
GEYA Optical Proximity Sensor Technical parameters：
| Order No：GY-E3Z-LS61/GY-E3Z-LS81 | |
| Technical parameters | |
| General instructions | |
| Output type | NPN NO+NC or PNP NO+NC |
| Detection method | BGS/FGS |
| Rated operating distance Sn | 30cm |
| Standard detection target | White paper 100×100mm |
| Rated grade | |
| Rated voltage UB | DC12-24V pulse (P-P) below 10% (10-30V) |
| Response time | <1ms |
| No-load current lo | <20mA |
| Voltage drop Ud | Below 2VDC (when the load current is below 100mA) |
| Working current IL | ≤100mA (with overload protection) |
| Circuit protection | Short circuit protection, power reverse polarity protection |
| Switch status indication | Operating indicator: red LED; power supply, stability indicator: green LED |
| Surroundings | |
| Ambient temperature | Operation: -25°C~+55°C (no freezing)/35~85%RH (no condensation) |
| Ambient temperature and humidity | Storage: -25°C~+70°C (no freezing)/35~95%RH (no condensation) |
| Ambient lighting | Sunlight: 10,000Lx Incandescent: 3,000Lx |
| Mechanical characteristics | |
| Wiring form | PVC lead-out type 2m (standard type) |
| Case material | ABS |
| Inductive surface | Optical PMMA |
| Protection level | IEC IP67 |
| High voltage resistance | 1000VAC,50/60Hz for 1 minute between charged parts and the case |
| Insulation resistance | More than 20MΩ (DC500V shaker) between charged parts and case |
| Vibration resistance | Durability: 10～55 Hz amplitude 1.5mm X, Y, Z each direction 2H |
| Shock resistance | 500m/s2 X, Y, Z each direction 3 times |
| Certifications and Standards | |
| Product cetificates | CE CCC CQC ISO9001 |
| Standards compliant | EC/EN 60947-5-2:2004 |
Magnetic proximity sensor
5. Magnetic Proximity Sensor
The magnetic proximity sensor works using the attraction between the magnet and target object to detect presence of an object. One of the advantages of these sensors is that they can detect magnetic targets through non-metallic materials, such as plastics and wood. They also have a fairly long sensing range.
So, how does a magnetic proximity sensor work? This sensor can be different types, and its working is based on the type of technology used. The types of magnetic proximity sensors include: reluctance based, reed switch type, magneto-resistive, Hall Effect sensor, and GMR (giant magneto resistive).
Variable reluctance sensor: this sensor consists of a permanent magnet and a pickup coil around a magnetic pole piece, and works by measuring the variations in reluctance.
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- Reed switch sensor: the magnetic reed proximity sensor consists of two ferromagnetic contacts housed in a sealed glass envelope. When a magnet is brought close to the sensor, it causes the reeds close and completes a circuit.
- Hall-effect sensor: this type of sensor works by measuring the changes resistance in a ferromagnetic material when a magnetic field is applied to it.
- Magneto-resistive sensor: these sensors work by sensing the variations in electrical resistance caused by the presence of a magnet close to it.
- GMR (giant magneto resistive) sensor: this type of sensor primarily comprises ferromagnetic plates separated by a non-magnetic spacer. When a magnet is brought close to the sensor, it causes a change in resistance that triggers a circuit.
- Application: Magnetic proximity sensors are commonly used as position sensing devices in industrial machinery, automotive components such as the crankshaft, and other machinery. Other applications include robotics and safety systems. These types of proximity sensor offer easy operation, and can be used in tough environments such as contaminated or high vibration situations.
GEYA Magnetic Sensor Technical parameters：Order No：GYBG4-M8-NA/GYBG4-M8-NB/GYBG4-M8-PA/GYBG4-M8-PB/GYBG4-M8-DA/GYBG4-M8-DB Technical parameters General instructions Output type NPN NO、NPN NC、PNP NO、PNP NC、DC NO、DC NC Installation method Non-flush mounting Rated operating distance Sn 4mm Raliable operating range distance Sa 0..3.2mm Standard detection target 12*12*1t(Q253A) Rated grade Rated voltage UB 10…30VDC Switch frequency f 1KHz Hysteresis range 1-15%of detection distance Repeatability <3%of detection distance No-load current lo <15mA Leakage current Ir <100uA Voltage drop Ud DC three-wire<2V,DC two-wire<3V Working current IL <100mA Circuit protection Reverse polarity protection,output short circuit protection,surge absorption Switch status indication Red LED indicator Surroundings Ambient temperature -25℃…70℃(248.…358K) Temperature effect -25℃…70℃,detection distance within 10%at +24℃ Environment humidity 35…95%RH Voltage influence <3% Mechanical characteristics Wiring form Standard wire length 2m Case materia Brass nickel plating Inductive surface PBT Protection leve IP66 High voltage resistance 1000VAC,50/60Hz for 1 minute between charged parts and the case Insulation resistance 50MΩ or more(DC500V)for the charged parts and case Vibration resistance 10～55 Hz,amplitude 1.5mm X,Y,Z each direction 2H Certifications and Standards Product cetificates CE CCC CQC ISO9001 Standards compliant EC/EN 60947-5-2:2004
How to choose a suitable proximity sensor?
To choose a suitable proximity switch, it is necessary to clarify the corresponding application requirements:
- Detection Target
The material of the object you’re trying to detect is crucial.
- Metal: If you need to detect metal, inductive sensors are a reliable and cost-effective choice. Capacitive sensors can also detect metal, offering more flexibility if you need to detect both metal and non-metal objects.
- Non-metal: For non-metal objects, the best sensor depends on the specific material and your working environment:
Capacitive: Great for liquids, powders, and materials with varying densities.
Ultrasonic: Works well with a wide range of materials, including those that are transparent or absorb sound.
Photoelectric: Ideal for detecting very small objects or objects with varying colors and surface finishes.
- Sensing Distance
Once you know what you’re detecting, consider how far away the object will be:
- Short Distance (a few millimeters): Inductive or capacitive sensors offer precise detection at close range.
- Medium Distance (a few centimeters): Ultrasonic and photoelectric sensors are reliable choices for this range.
- Long Distance (over tens of centimeters):
Long-range photoelectric sensors: Use a focused beam of light for detection over large distances.
Laser distance sensors: Provide highly accurate measurements over long distances.
- Response time:
How fast does your application require a response speed?
- Fast response (a few milliseconds): Inductive sensors have the shortest response time
- Medium response (tens of milliseconds): Capacitive and photoelectric sensors can meet most application scenarios
- Slow response (several hundred milliseconds or more): The response time of ultrasonic sensors is slow, suitable for some scenarios that do not require fast response
4.Environmental conditions:
What environment does the proximity sensor work in?
- Temperature: It is necessary to ensure that the temperature of your usage scenario is within the working temperature range of the sensor
- Humidity: Select sensors with appropriate protection levels to prevent proximity switches from being affected by humid environments.
- Dust, vibration, and impact: Select sensors with sufficient protection levels based on the severity of the environment.
5.Output signal:
What kind of output signals does your control system require?
- Digital output: Provides ON/OFF signals, suitable for simple detection scenarios.
- Analog output: provides a continuous signal proportional to the distance to the target, suitable for applications that require distance information
6.Cost budget:
How much budget do you have for sensors?
- Inductive sensors: usually the most cost-effective choice.
- Capacitive sensors: affordable price and more diverse functions.
- Ultrasonic and photoelectric sensors: usually more expensive.
The following is a brief table summarizing the advantages and disadvantages of different types of proximity sensors:
|
type |
advantage |
shortcoming |
Typical applications |
|
Inductive type |
Low cost, fast response speed, strong anti-interference ability |
Can only detect metal objects |
Object counting, position control, presence detection |
|
Capacitive type |
Can detect metal and non-metal objects, insensitive to environmental changes |
The sensing distance is greatly affected by the target material |
Liquid level detection, material detection, proximity switch |
|
ultrasonic |
Can detect various materials, unaffected by color or transparency, measurable distance |
Slow response speed and susceptibility to environmental noise |
Distance measurement, obstacle avoidance, liquid level control |
|
Photoelectric type |
Long detection distance, high accuracy, and fast response speed |
Vulnerable to environmental light interference and requiring clear line of sight |
Object counting, position detection, barcode scanning |
Common brands and models of proximity switches
- GEYA:
Brand advantage: A Chinese brand known for its high cost-effectiveness, reliability, and extensive product line.
Recommended model:
GYBT15-M30: Detection distance 15mm, NPN/PNP/D: DC: 10… 30VDC, AD: AC/DC: 24-250V, 360 ° visible indicator light
GYAT1.5-M8: Using durable, oil-resistant wire， The detection distance is 1.5mm.
GYBG16-M18: IP66, detection distance 16mm
- Omron:
Brand Advantage: A Japanese brand known for its high quality, ease of use, and cost-effectiveness.
Recommended model:
E2E-X10C1: Long-distance inductive proximity sensor, with a detection distance of up to 10mm and an IP67 protection level.
E2A-M18KS08-WP-C1: High temperature resistant inductive proximity sensor, suitable for high-temperature environments, with a detection distance of 8mm.
E2K-C04MC1: Capacitive proximity sensor, capable of detecting liquids, with a detection distance of 4mm.
B5W-LA415: Optical sensor, compact in size, with a detection distance of up to 5m.
- IFM:
Brand Advantage: A German brand known for its high-quality, innovative technology, and easy-to-install products.
Recommended model:
IGT202: Small inductive proximity sensor with a detection distance of 2mm, suitable for small spaces.
IFR201: Capacitive proximity sensor, capable of detecting both metals and nonmetals, with a detection distance of 10mm.
UCG252: Ultrasonic sensor with a detection distance of up to 250mm, suitable for distance measurement and liquid level control.
O1D100: Optical sensor with a detection distance of up to 100mm, suitable for object detection and counting.
Application of proximity sensors
Here are some practical application cases of proximity switches:
- Industrial automation:
- Accurate object counting on production lines: Sensors track passing items, aiding output monitoring and quality control.
- Precise robotic arm movements: Sensors guide robotic arms for accurate grasping, placement, and welding.
- Real-time liquid level monitoring: Sensors in storage tanks enable automatic filling/discharge and prevent spills.
- Enhanced workplace safety: Sensors create “safety light curtains” that detect intrusions and halt equipment, protecting personnel.
- Automotive industry:
- Aiding parking: Ultrasonic sensors in bumpers measure distance to obstacles, assisting drivers with parking.
- Monitoring engine speed: Magnetic sensors track engine speed for control systems and speedometers.
- Detecting door status: Sensors on doors control interior lighting and enhance anti-theft systems.
- Consumer electronics:
- Enabling smartphone features: Sensors turn off screens during calls, saving power and preventing accidental touches.
- Powering smart homes: Sensors automate door locks, lighting, curtains, and more, creating a seamless living experience.
- Guiding robot vacuums: Sensors help robot vacuums navigate obstacles, ensuring efficient cleaning.
- Other fields:
- Healthcare: Sensors in medical devices monitor vital signs like breathing and heart rate, aiding diagnosis and treatment.
- Aerospace: Sensors ensure flight safety by monitoring fuel levels, door status, landing gear, and other crucial parameters.
- Food processing: Sensors optimize production by precisely detecting objects for tasks like packaging and cutting.
Conclusion
Different types of proximity sensors are built to accommodate different applications. The choice of the type of proximity sensor depends on the specific requirements of the project. Based on the application, one can select a suitable sensor with the right accuracy and range. Inductive and capacitive sensors are the most used types, so your choice will most likely be one of these.
