In the pharmaceutical, building materials and food industries, on vessels and silos, on platforms and dosing systems, right up to kitchen and bathroom scales ? weight is measured everywhere. In industry, it becomes particularly interesting when it comes to the level in vessels. There are various possibilities for weight measurement or weighing. The filling level could be determined optically, hydrostatically, by ultrasound, microwaves and radar, mechanically, capacitively, by heat dissipation, by displacement and resistance or, what this short article is about, gravimetrically.
The term gravimetric comprises the Latin ?gravitas? for ?gravity? and the Greek ??? ??????? for ?measure?. In gravimetric measurement, therefore, the heaviness of the mass is combined with weight force to form a meaningful value and therefore the level is determined by weighing vessels (the filling level results from the density of the medium and the geometry of the vessel). Left Behind makes gravimetric level measurement part of weighing technology.
Gravimetric level measurement is particularly suitable when uneven distribution may appear within the vessels.
Gravimetric level measurement: Advantages
This kind of weighing has several advantages. Perhaps the greatest advantage is that the force transducers useful for gravimetric level measurement can be found beyond your vessel. Thus, they do not touch the product. Nor is it necessary to open or modify the vessels. Contamination can thus be eliminated. Cleaning can be much easier. Furthermore, very precise measurement can be done ? 0.02 % of the rated load isn’t uncommon regarding relative linearity error. This makes dosing possible when, for instance, food is filled into bags ? and of course the packaging must contain the amount specified.
Another advantage is that the merchandise does not influence the measurement. The level can be determined gravimetrically for all contents ? solids, liquids, viscous substances, foaming substances ? even toxic or aggressive contents can be viewed as. Furthermore, the measurement isn’t falsified even if voids or uneven contents distribution occur inside the silo or tank, because the entire contents are weighed.
Suitable mounting modules not merely ensure that the weight force is properly led in to the force transducers, in addition they make installation super easy. The module and force transducer have a minimal height and a small installation volume. However, it might be problematic if the vessels are already permanently installed and will only be placed on modules with a great deal of effort. Then it really is probably advisable to bolt strain transducers to the supports. Any risk of strain transducers determine the compression of the supports due to the weight of the contents. They thus be able to weigh immovable vessels gravimetrically.
Gravimetric level measurement: Disadvantages
The disadvantages of gravimetric level measurement vary in significance depending on the application. Email address details are mainly distorted when force shunts can’t be prevented. Ideally, the vessel should be mechanically decoupled. In practice, however, it can always happen that, for example, struts are essential. Then it depends on how great their supporting effect is. Similar problems may appear if the measurement is influenced by a high bearing weight. The low the weight of the vessel when compared to product, the more accurate the gravimetric measurement. Finally, free-standing outdoor vessels can be affected by natural factors. For example, if wind pushes or snow leads to a significant increase in weight.
Typical force transducers for the weighing of vessels
Single point load cells are classically useful for scales. These not merely have a low price and high accuracy, however the weight can be determined reliably, no matter where it is placed on the platform. For optimal force introduction, bending or shear beams with the corresponding weighing modules are usually installed under tanks, silos or vessels that stand on supports. To determine the rated load of the force transducers, divide the full total weight of the vessel by the number of supports. If the rated load exceeds 10 t, you’ll be able to switch to compression force transducers, the utmost capacity which reaches around 300 t. With four supports, vessels of up to 1,200 t can be weighed with the best accuracy. Alternatively, vessels can be suspended from S-type force transducers or fitted with strain transducers.
Note
Level could be measured in many various ways. Whether gravimetric as described, or with a submersible pressure sensor, float switch or pressure sensor ? WIKA has the right sensor for every application. Do you want to buy the products? In our WIKA online-shop you will discover a few of our standard designs. When you have any questions, your contact will gladly assist you to.
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