How do non-contact sensors work, and what benefits do they offer to machine builders?

Non-contact Sensors: Operation and Benefits for Machine Builders

Depending on the intended purpose, sensors operate based on various principles such as conductivity, pressure, acceleration, or chemical composition. This blog focuses on non-contact sensors, exploring what makes this group special, how they work, and what specific advantages they provide.

Traditionally, sensors make physical contact to measure the desired quantity, involving mechanical interaction between the sensor and the target. Examples of this sensor type include temperature sensors (thermocouples), strain gauges, pressure sensors, and tactile sensors.

These so-called contact sensors are reliable and accurate but have the disadvantage of experiencing wear over time due to the contact. This can lead to a decrease in accuracy and reliability. Additionally, these contact sensors are unsuitable for measuring moving objects or substances where contact is undesirable, such as dangerous, toxic, or aggressive substances, or when the target is simply not within the sensor's range.

Non-contact Sensors

For specific applications, non-contact sensors provide a solution. They eliminate wear by lacking physical contact and utilize principles such as heat and light radiation, gravity, acceleration, sound, magnetism, and electric fields.

Inductive Sensors

Inductive sensors generate a high-frequency electric field. When metal enters this field, eddy currents are formed, damping the field. The closer the metal is to the sensor, the higher the damping. This type of sensor is mainly used for detecting metals at short distances.

Capacitive Sensors

A capacitive sensor operates similarly to an inductive sensor but utilizes a high-frequency oscillator that generates an electric field through a capacitor. This field changes when any substance comes near, making these sensors suitable for detecting both conductive and non-conductive materials. Applications include touchscreens.

Magnetic Sensor

Magnetic sensors operate based on the magnetic field established between the sensor itself and a permanent magnet. The field changes when an object moves between the sensor and the magnet. These sensors are used for magnetic door switches and compasses. Additionally, there are magnetic non-contact sensors that determine the orientation of a permanent magnet within a certain distance from the sensor.

Ultrasonic Sensors

Also contactless, sensors working on high-frequency sound waves measure the time these waves take to bounce back from an object. With this, these non-contact sensors can measure distances and detect presence.

Infrared Sensors

Infrared is thermal radiation, and infrared sensors are used to detect the presence or movement of objects. The active form emits infrared radiation and reacts to the radiation reflected by an object. The passive form responds to the infrared radiation emitted by any object. Infrared sensors can detect movement and are used in estimating distances.

Laser Sensors

To measure distances or detect objects, laser sensors emit a focused laser beam. Various laser sensors are available, some based on the time the beam takes to return. Others are used for creating projections or establishing a certain safety level: interrupting the beam (or an entire curtain) means that something or someone is entering an area where it shouldn't, prompting a safety control to stop or secure the relevant application. A significant limitation of laser sensors is that the reflective surface and the receiver are sensitive to pollution.

Acceleration Sensors

Accelerations resulting from gravity or movement generate a G-force that can be measured without contact using acceleration sensors. This type of non-contact sensor can be used as a level, accelerometers, or tilt sensors that switch at a specific G-force. In addition to their non-contact nature, these sensors offer the advantage that the designer has the freedom to mount the sensor in any location. Applications of these sensors can be found in the mobile machinery market.

DIS Non-contact Sensors

DIS offers two types of non-contact sensors: the QG series inclinometers, tilt switches, and accelerometers, and the QR series angle sensors. 

QG Series Sensors

The QG series sensors includes inclinometers measuring inclinations in 1 or 2 axes, as well as tilt switches and accelerometers measuring accelerations in 1, 2, or 3 axes. A tilt switch activates at a certain angle relative to the horizon, essentially functioning as an inclinometer with a switch output.

All types are based on robust MEMS technology, where capacitance differences within a micromechanical sensor chip are converted into an analog voltage. This voltage is proportional to the acceleration the sensor is exposed to. The modular design allows easy customization of sensors to specific requirements.

QR Series Angle Sensors

With the QR series angle sensors, it's possible to measure absolute angle rotation from 0° to 360° without mechanical end stops. In the QR30N and QR40EMN series, the sensor and magnet are separated by a maximum distance of 10 mm. In the QR40 and QR46 series, the magnet is integrated into the rotating shaft within the housing.

Both series are available as absolute angle sensors, where the sensor retains the exact angle position even when the application has been without power. The QR30 series is also available as an incremental sensor with an external magnet, generating a certain number of pulses with each angle rotation. These non-contact sensors from the QR series can be used as alternatives to potentiometers, expensive optical encoders, and rotary switches, particularly in general industry and automotive applications.

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