Measuring filling levels in automated Industry 4.0

Waycon Positionsmesstechnik GmbH is ideally equipped for the future

An automated measurement of substance filling levels in storage containers is essential in Industry 4.0. For a secure and stable production process, continuous monitoring of filling levels is an absolute prerequisite. Waycon Positionsmesstechnik offers needs-based, automated monitoring of filling levels for many industries.

These can be split into two main types:

·         Monitoring the filling level for the feeding and timing of the filling process as well as the retrieval of stock status.
·         Initiating safety measures (e.g. shutting down) when a maximum or minimum filling level is reached

In the first case, we are talking about continuous filling level control. The filling level of the monitored substance can be registered at any time at any position in the container and ensures a continuous reading. The advantage of this is that capacity planning can be adapted for irregular use at any time in the production process.

In the second case, we are dealing with a “level detection”. Predefined maximum and/or minimum filling levels are defined and monitored throughout the production process. If the relevant level limit is exceeded or too low, an action is initiated. This monitoring method is best suited to continuous processes for the timely supply or removal of necessary substances. The level detection also serves as a safety measure, for example to avoid overfilling due to system shut down.

The different methods of filling level measuring
Filling level measuring works via contact or non-contact sensors which determine the distance between the sensor and the object being measured.

Ultrasound filling level measuring
Classic filling level measuring works with the help of ultrasound sensors. Measurement with ultrasound sensors is a non-contact method and is suitable for both continuous filling level control and level detection. Ultrasound sensors release high frequency oscillations, which are reflected through the object being measured. The time difference between the moments of “sending and receiving” is calculated. The advantage of this method is that it is not dependent on the substance used, e.g. oil or water.

Measuring filling level with the magnetostrictive principle
Magnetostrictive sensors are non-contact and free from wear.  A short, constant electrical pulse is sent via a waveguide. A freely moving position magnet reacts to the electrical pulse with a reversed torsion wave. Moving the position magnet produces a different run time for the response pulse. With the help of a pulse converter, this is finally converted into an electronic measurement signal. The magnet is embedded in a float and guarantees permanent registration of the filling level. Magnetostriction is non-contact but the float must make contact with the substance being measured.

Filling level measuring using draw wire sensors
Draw wire sensors are a contact measurement method. A stainless steel wire is coiled in a single layer around a drum with a pre-stressed mainspring. The measurement wire is attached to the object being measured and the is drawn from the drum if the position is changed. The drum’s axis is firmly attached to an electronic element, which converts the mechanical turning movement into a proportional electronic signal. For the filling level measuring, the measurement wire is connected to a float which is in contact with the measuring material.

Filling level measuring with the capacity principle
Capacity sensors measure changes in capacity. Thus the sensor and the object being measured always create a plate, as you find with a plate capacitor. The electronic field in between them is recorded and changes according to the distance. This measurement method is non-contact and is suitable for continuous monitoring and level detection.

WayCon offers suitable measurement engineering for all uses
With WayCon’s intelligent sensor solutions, measuring filling levels is easy and efficient. The Taufkirchen company’s broad production spectrum can be used in practically any industry and for any use. Companies are already equipped for Industry 4.0 with WayCon sensors for their filling level measuring.

You can find more information at www.waycon.de/home/ or

Product portfolio: www.waycon.de/produkte

Ultrasound in the animal world

Our distance and proximity sensors work with the ultrasound principle. We use ultrasonic frequencies, i.e. frequencies above 20kHz, as these are rare in nature and thus the sensors are not disturbed. Moreover, man hears no such high frequencies. Incidentally, they are also completely harmless, because the sound energy is extremely small. Industrial ultrasonic sensors operate at frequencies of approximately 80…400kHz, depending on what characteristics the sensor shall have. The greater the required measuring distance is, the lower frequencies must be used.

Few creatures also make use of ultrasound for guidance. These are mainly the dolphin (in water) and the bat (in the air, as our sensors). Both have bad organs of sight and send ultrasonic waves up to 200kHz. In addition, also other creatures can hear frequencies above 20 kHz although they probably don’t have a benefit for their orientation:

Man 20kHz, Dog 50kHz, Cat 60kHz, Grasshoper 95 kHz, Shrew 115kHz

The dolphin transmits and receives ultrasonic waves in water in order to detect obstacles and beasts of prey. Since the acoustic impedance of water is about 3000 times higher than that of air, both waves generated by animal as well as by technique reach much farer in water than in air.

For the bat living in air it is more difficult. Its high-frequency sound waves do not extend so far. But it also has the most advanced ultrasonic location system. The high frequency enables it to get a very fine local resolution. The ultrasonic cries of bats are produced in the larynx and emitted through the mouth to the outside. When the emitted waves meet a flying body, e.g. a small prey animal, they are reflected and returned to the ears, which serve as a sound signal receiver. The hearing organs of bats must have an amazingly good sound analysis capability. It is believed that due to only microsecond short differences in time of sound flight between the left and right ear they are able to get a three-dimensional acoustic image. Therefore a bat can orient itself with their ears in the absolutely dark, as we do with our eyes at daylight.

As engineers we need to give us once more defeated by nature.

Ultrasonic sensors in road and tunnel construction

During the construction of major highway and railway projects, particularly in tunnel construction, huge quantities of excavation occur. When the mining takes years, it is worth to use giant conveyor belt systems. Such installations may be several kilometers long and have a capacity of more than 1000 tons/hour. These belts are of course fully automated. This creates the risk that the excavation blocks the hopper at the transfer points from one band to another.

For permanent monitoring of the transfer stations robust ultrasonic sensors are used. They look down into the hopper and report if the level exceeds a certain value. The plant will then be slowed or stopped accordingly. Suitable ultrasonic sensors from Waycon Positionsmesstechnik are those of the UN series. The outstanding feature of the UN series is its high acoustic power combined with small sensor size. This is achieved with new optimized SONARANGE transducers, working at high electrical voltages. Thus also small, moving and poorly reflecting objects can be safely detected. Moreover the sensors work also under high contamination. With a length of <40mm the UN sensors are the most compact ultrasonic sensors for such high measuring ranges.

Langzeitversuche mit Ultraschallsensoren

Ultraschallsensoren werden dank ihres vorteilhaften physikalischen Prinzips häufig dann eingesetzt, wenn zum Beispiel optische Sensoren wegen starker Verschmutzung oder rauem Umfeld nicht mehr zuverlässig funktionieren. Umso mehr ist darauf zu achten, dass die Sensoren auch von der Elektronik und Mechanik her auf Robustheit und lange Lebensdauer ausgelegt sind.
Die Geräte sind ununterbrochen eingeschaltet und  werden periodisch ausgemessen. Mittlerweile sind bei einigen Sensoren 65’000 Stunden aufgelaufen, und sie messen noch wie am ersten Tag. Neben den Elektronikkomponenten ist der Schallwandler das heikelste Teil. Er stellt eine akustische Membrane dar, die ca. 30mal pro Sekunde elektromechanisch angeregt wird. Die Amplitude im Zentrum wurde als ein paar wenige Mikrometer gemessen und die Sendedauer für einen Puls beträgt ca. 0.1 Millisekunden. Bei einer typischen Ultraschallfrequenz von 200kHz ergibt sich damit eine während dem Langzeitversuch aufgelaufende Anzahl Membranschwingungen von etwa 10¹¹. Das sind 100 Milliarden Schwingungen. Die Membrane, von der man nicht wahrnimmt, dass sie sich bewegt, hat sich in der Zeit gut 200km hin und 200km zurück bewegt.
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Ultrasonic sensors are often used thanks to their advantageous physical principle when, for example, optical sensors do not work properly due to heavy dirt or rough environment. All the more it is important that the sensors electronics and mechanics are tuned for ruggedness and long service life.
The devices are permanently turned on and they are checked periodically. Meanwhile, some of the sensors have accumulated 65’000 hours, and they measure the same as on the first day. Besides the electronic components, the ultrasonic transducer is the most critical part. It represents an acoustic diaphragm which is electromechanically excited approx. 30 times per second. The amplitude in the center was measured as a few micrometers. And the transmission duration of one pulse is about 0.1 milliseconds. Thus with a typical ultrasonic frequency of 200kHz the accumulated number of membrane oscillations during the whole endurance test is around 10¹¹. That’s 100 billion oscillations. The membrane, of which one does not perceive that it is moving, has passed 200km forth and to 200km back in this time.