Distance sensors, as the name suggests measure accurate distances between objects. There are different types of distance sensors which provide different benefits. Some of them are as follows:

Radar distance sensors

Radar distance sensors use radio waves and microwaves. These waves are directed at various objects and are then reflected back to the source. The distance to the object is then measured depending upon the time required for the signal to return.

Sonar

Sonar is known for accurate and reliable distance measurement. Sonar works in a similar way to radar. However, it makes use of sound instead of microwaves. Sonar is mostly used in submarines and other such underwater applications. The idea of sonar was developed from land animals like bats which make use of a natural form of sonar for navigating and avoiding collisions.

Proximity distance sensors

This particular sensor operates by projecting a directed beam. The sensor then senses the change in deflection of the beam to measure the distance of a measured target. Proximity distance sensors are available in many different designs including photocell and thermal sensors.

Laser range finders

In laser range finders, information is collected by directing a laser beam at an object. Hand-held laser range finders are also available these days.

The ultrasonic proximity sensor is used for measuring distance without making contact with the target. They work by the emission of a short wave sound burst. The ultrasonic sound wave will reflect back to the source. And, the time taken for the echo/ return time is calculated by the system and the distance is calculated.
The calculation and analysis of an ultrasonic sensor is based upon the speed of sound. You will need to consider the following acoustic variances before selecting a non-contact ultrasonic proximity sensor.

Acoustic variance is caused by the following factors

The speed of sound changes under the effect of temperature and density of the medium. So you need to consider the inconsistency of the readings you receive. Let us have a look as some other factors which may affect the accuracy of distance readings. Another common factor which can create discrepancies in a reading is excessive background noise. Background noise affects the frequency of the sound and makes changes in the upper and lower distance measurement limits of the sensor.

The frequency of emitted sound and its speed

The accuracy of the reading will get affected adversely by the combination of frequency and speed of sound. These factors make a significant change in the upper and lower target distance limits of the sensor.
How does humidity affect your readings?

The frequency of the sound wave can be affected by humidity in air and cause the magnitude of sound to become lower. Humidity may thus affect the maximum target distance capacity of the sensor.

Ultrasonic proximity sensors are used for non-contact distance measurement. Ultrasonic proximity sensors emit a shortwave burst of sound towards the target. This ultrasonic sound wave reflects back to the source. The echo return time is analysed by the system to give us the distance from the source. This calculation uses the speed of sound in the calculation. Ultrasonic proximity sensors can be selected depending on their specific purpose and mechanical requirements.

Mentioned below are the important variables which need to be assessed while purchasing an ultrasonic proximity sensor:

Temperature and density

Density of the medium and temperatures cause a change in the speed of sound. The resulting effect on accuracy must be assessed.

Speed of sound and frequency

The sound speed and frequency have an interrelationship with wavelength and this affects the upper and lower limits of the target distance and the final accuracy.

Effect of humidity

Humidity in air and frequency reduce the magnitude of sound and affect the upper limits of the target distance. This variance must be eliminated.

Effect of background noise

Frequency changes the levels of background sound and it affects the upper limit of target distance. The lower limit for target size must thus be observed.

Pattern of sound radiation

If there are changes in the beam angle of the ultrasonic transducer as well as the sensor system they may influence the maximum target distance. By eliminating this error, we can eliminate the possibility of hitting an unrelated target.

Effect of target specifications

The effect of distance, target surface, surface size and its dimensions on the maximum target distance possible with the sensor will reflect in the strength of the echo. This difference must be compensated for.

A sensor can be termed as a device that measures a physical quantity and converts it into a signal that is easy to read for an observer or computer.

There are a number of distance sensors available on the market. It is important to identify the right type. Mentioned below are some questions you need to ask before opting for a distance sensor.

• How much space can be allocated to these devices?
• What is the resolution that you require?
• What is your target material?
• What should be the range for your target machine?

Based on the above questions, you can opt for a distance sensor that is best suited to the needs and requirements of your business.

Inductive sensors

The measuring principle of these sensors is based on the evaluation of inductive eddy currents. Therefore inductive sensors work best on electrically conductive metal targets such as steel, metallic alloys and aluminium. These sensors are known to be resistant against non-metallic environmental contaminants that include dust, oil and cutting fluids.

Ultrasonic distance sensors

Ultrasonic distance sensors offer distance measurement with the help of ultrasonic transmission. These sensors are capable of offering resolutions up to >0.3 mm based on the speed of sound through air. Ultrasonic distance sensors also measure the time required for the sound to return to the sensor.

Optical distance sensors

Laser interferometers, diffuse sensors and fibre optics are some of the different ways of optically sensing distance. Interferometers offer nanometre resolutions and long sensing ranges, but are expensive and require complex peripherals and optically efficient targets.

The aforementioned distance sensors will help you determine the type that is best suited to your needs and requirements.

If you are looking for a distance sensor, it is important to understand the different types available.

Inductive distance sensors

If your business uses electrically conductive metal targets such as steel, metallic alloys or aluminium, it is advisable to opt for inductive distance sensors. This is because the measuring principle of inductive distance sensors is based on the evaluation of inductive eddy currents. These sensors are resistant to all kinds of non-metallic environmental contaminants including dust, cutting fluids, and oil.

Ultrasonic distance sensors

Certain types of distance sensors offer a distance measurement with the help of ultrasonic transmission. Ultrasonic distance sensors are capable of measuring distance by calculating the speed of sound and the amount of time it takes for sound to return to the sensor. Ultrasonic distance sensors offer resolutions of up to >0.3 mm. The major benefit of ultrasonic distance sensors is their ability to measure difficult targets such as solids, liquids, granulates and powder.

Optical distance sensors

Laser interferometers, diffuse sensors and time-of-flight sensors are some of the many optical distance sensors available. Laser interferometers offer high resolution along with high sensing ranges.

Diffuse sensors can be programmed to offer rough distance measuring. However, they require target colour and reflectivity to accurately measure the distance as they operate on the intensity of light received.

On the other hand, time-of-flight sensors feature long measuring ranges and self contained packages but rely on propagation time. These sensors offer a limited resolution of 3-5 mm over their measuring range.