In much processes there is the demand for automation in the form of a distance measurement. This provides more grip and insight in the process. In addition, the accuracy, reliability and efficiency increase. Examples of these are:
- A truck that backs up towards a loading bay
- Determining the position of a gripper towards a container
- Determining the distance of a ship to a quay, mooring and berthing
- Level measurement in a bunker
- Level measurement in a tank
These are all great applications, but which sensor is the right choice? What is this choice based on?
In this article we discuss the differences between the ultrasonic- and laser-based measuring principles, the challenging applications that emphasise those and an overview of possible solutions.
Wat is laser light?
Laser is light, but very intense. This is because the light particles in laser light are much closer together than in regular lighting. A characteristic of laser sensors is that laser sensors are made both in the visible spectrum and in the invisible spectrum. That means there are infrared as well as visible red lasers. Laser light can be used to accurately measure very small but also very large distances. Methods that are applied here are: “Time of Flight” and the “phase shift”.
Lasers have to follow the same rules as normal light which makes the advantages and disadvantages somewhat similar. Advantages are, but not limited to, a high speed, very high precision and a sharp focus on small surfaces. When it comes to measuring size, lasers are applicable over very small as well as very large distances.
The disadvantages of the use of light are the susceptibiliy to ambient light, the (limited) reflectivity or too much relief on the measurement/detection surface and objects that let through light. These can all form an obstacle for the emitted light of the sensor.
What is ultrasonic sound?
Ultrasonic is an area within the sound spectrum. In other words: vibrations that move through the air. What characterizes ultrasonic sound is that it can not be perceived by the human ear. In nature, this sound spectrum is used by dolphins and bats, for example. Specifically in order to detect, communicate and determine distances to objects.
The use of sound brings advantages but also some downsides. The advantages consist of: insusceptibility to color, gloss and transparency of objects, a very good measurement on solids and liquids and no hindrance in measurements of objects with a coarse or fine structure.
When it comes to disadvantages, ultrasonic sound has a smaller range and a greater susceptibility to sound-absorbent materials or surfaces like foam and textile.
What are the applications that require laser light or ultrasonic sound?
The aforementioned fundamental description of ultrasonic sound and laser light help in translating these properties to usable practices. Below are a number of industrial applications where ultrasonic sound or laser light provide a solution.
Measurement of transparent objects
Transparent objects such as a plastic bottle have the property of letting through light. If a laser would be used to measure the distance to the bottle it would encounter issues because of the lack of a reflection of the laser light that has to be received by the sensor. An ultrasonic sensor, however, is a very suitable solution for this: the emitted sound does not go through the packaging and thus is reflected. This allows the measurement to be performed, so the sensors can determine the distance to the bottle.
High accuracy
Sometimes a measurement has to be performed on surfaces that are very variable in shape. Think of tire profiles that have to be measured from a distance. The use of an ultrasonic sensor is less suitable here, because the greater the distance, the less precise the measurement. Laser light, on the other hand, has the necessary precision to reach and thus measure these openings. This allows the tire profile to be determined down to micrometers, so that wear or product errors can be traced.
Measurement on different colors
In the packaging industry, materials and product packaging come in all kinds of different colors. Not every color has the same reflectivity, which means that one color reflects more than another. We often notice this when wearing a black shirt on a summer day: we experience the sun even hotter than someone with a white shirt. This is due to the degree of reflection. The laser light, just like any kind of light, is subject to this because not every color reflects an equally good reflection back to the sensor. An ultrasonic sensor therefore is prefered which is insensitive to the color of a package.
Measurements on a (very) large scale
The range is perhaps the most important factor when it comes to a (distance) measurement. Ultrasonic sensors reach up to 8,000 mm (or 8 meters) and thus can be used within most small and medium distances. The laser sensors start at a maximum measuring range of 10 cm and are available up to even a 3,000 meters (or 3 km). Distance lasers can be used for small, medium and (very) large distances. Think of a level measurement in a silo.
Sound-absorbing materials
In the textile industry, all kinds of materials are used from cotton to wool and from synthetic materials to unprocessed fabrics. Materials with an open structure often have a sound-absorbing property. This ensures that when measuring with an ultrasonic sensor, the sound vibrations are reflected less or not at all to the sensor. It seriously affects the measuring range. The laser is a common solution here because it can perform error-free measurements on these types of materials, without significant influence on the measuring range (apart from the color).
What to choose?
Below we have arranged the ultrasonic and laser sensors that we provide in fold-out tables and compared them in terms of measuring range, extras and usability in different applications.
| Measuring range | Extras | Usability in different applications |
Nano series | 350 mm | Smallest M12 ultrasonic sensor in the world | Measurements with small mounting space |
Pico+TF series | 1,300 mm | Teflon layer around transducer for chemical resistance | Measurements in environments with chemical materials |
UK6 series | 1,200 mm | Short-form plastic or metal M18 housing | For applications with less mounting space |
UK1 series | 2,200 mm | Cylindrical M18 housings made from plastic or metal with teach-in button | Simple teach-in for application on a larger scale |
UQ1 series | 1,200 mm | Cubical housing with M18 sensor head | For applications with a right-angled mounting |
Lpc+ series | 1,000 mm | Temperature compensation for automatic adjustment to the ambient temperature and an IO-Link interface. | Middle-range distance measurements; |
Nero series | 1,000 mm | Plastic M18 housing, available in normal and right-angled housing | Middle-range ultrasonic distance measurements |
Crm+ series | 6,000 mm | Special protective foil layer over transducer | Big-range ultrasonic distance measurements |
Mic series | 6,000 mm | Stainless steel M30 housing for challenging environments and an automatic synchronisation when multiple sensors are used | Long-range ultrasonic distance measurements |
Mic+ series | 6,000 mm | Stainless steel M30 housing for challenging environments and an automatic synchronisation when multiple sensors are used | Long-range ultrasonic distance measurements |
Wms series | 6,000 mm | Trigger input and echo output functionalities | Long-range ultrasonic distance measurement |
Sks series | 150 mm | Very compact rectangular housing and IO-Link support | Critical ultrasonic distance measurements |
Zws series | 700 mm | Most compact rectangular ultrasonic sensors with a very high switching frequency (250 Hz) and teach-in button | For high-speed measurement applications |
Lcs series | 1,300 mm | Compact cubical housing, automatic synchronisation and multiplex mode | Middle-range measuring applications with multiple sensors |
Lcs+ series | 6,000 mm | Compact cubical housing, IO-Link support, automatic synchronisation and multiplex mode | Middle-range measuring applications with multiple sensors |
Hps+ series | 3,400 mm | PTFE-foil over transducer for protection against agressive chemicals, stainless steel housing, extra hygiene | Use in environments with agressive chemicals |
Pms series | 1,000 mm | ECOLAB-, FDA- and EHEDG-compliant housing | For use in environments with chemical materials, agressive cleaning agents and a highly approved hygiene |
LASE 1000 series | 110 m on natural surfaces and 800 m on a reflector | Support of multiple industrial interfaces and a very high measuring speed (20 kHz) | Applications with very high speeds, Integration in the most existing and new systems by supporting most common industrial interfaces. |
LAM 34 series | 30 m on natural surfaces and 250 m on a reflector | Very high switching frequency (30 kHz), eye-safe infrared laser | Applications where people often work near the laser; |
The LAM 50 series | 30 m on natural surfaces and 150 m on reflector | Options as an internal heating, multiple interfaces. | For use in applications with an ambient temperature starting at -40°C For integration in existing and new systems |
SP1200 series | 600 m on surfaces with limited reflectivity and 1,200 m on a reflector | Dot laser for visual alignment, very large measuring range | For large-range measurement applications |
The LAM 70 series | 70 up to 125 on natural surfaces and 270 m on a reflector. | Very compact housing, switching between multiple measuring points, modular functionality | Applicability as laser module in a LIDAR system |
The LAM 5 series | 5.11 - 6 meters | Cost-effective solution, | Less critical applications that require the advantages of lasers; |
LAM 300 series | 300 m on natural surfaces and 3,000 m on target board | Two switching outputs, which allows a window mode; | Applications over a very high measuring range such as a level measurement in a grain silo or the guidance for ships when berthing and mooring; |
