In the pharmaceutical, building materials and food industries, on vessels and silos, on platforms and dosing systems, right around kitchen and bathroom scales ? weight is measured everywhere. In industry, it becomes particularly interesting in terms of the particular level in vessels. There are many possibilities for weight measurement or weighing. The filling level can be determined optically, hydrostatically, by ultrasound, microwaves and radar, mechanically, capacitively, by heat dissipation, by displacement and resistance or, what this article is about, gravimetrically.
The term gravimetric comprises the Latin ?gravitas? for ?gravity? and the Greek ??? ??????? for ?measure?. In Unassuming , therefore, the heaviness of the mass is combined with weight force to form a meaningful value and therefore the level depends upon weighing vessels (the filling level results from the density of the medium and the geometry of the vessel). This 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 type of weighing has several advantages. Possibly the greatest advantage is that the force transducers useful for gravimetric level measurement are located outside the vessel. Thus, they don’t come into contact with the product. Nor is it essential to open or modify the vessels. Contamination can thus be eliminated. Cleaning is also much easier. Furthermore, very precise measurement is possible ? 0.02 % of the rated load isn’t uncommon with regards to relative linearity error. This makes dosing possible when, for instance, food is filled into bags ? and of course the packaging must support the amount specified.
Another advantage is that the merchandise will 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, Affordable isn’t falsified even if voids or uneven contents distribution occur in the silo or tank, because the entire contents are weighed.
Suitable mounting modules not only ensure that the weight force is properly led into the force transducers, they also make installation super easy. The module and force transducer have a low height and a little installation volume. However, it can be problematic if the vessels already are permanently installed and may only be positioned on modules with a great deal of effort. Then it really is probably advisable to bolt strain transducers to the supports. Wreaking determine the compression of the supports caused by 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 with regards to the application. Results are mainly distorted when force shunts cannot be prevented. Ideally, the vessel should be mechanically decoupled. Used, however, it can always happen that, for example, struts are absolutely necessary. Then it depends on how great their supporting effect is. Similar problems can occur if the measurement is influenced by a high bearing weight. The low the weight of the vessel compared to the product, the more accurate the gravimetric measurement. Finally, free-standing outdoor vessels could be suffering from natural factors. For instance, if wind pushes or snow results in a significant upsurge in weight.
Typical force transducers for the weighing of vessels
Single point load cells are classically useful for scales. These not merely have a minimal price and high accuracy, however the weight can be determined reliably, no matter where it is positioned 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 look for the rated load of these force transducers, divide the total weight of the vessel by the amount 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 as high as 1,200 t could be weighed with the highest accuracy. Alternatively, vessels can be suspended from S-type force transducers or fitted with strain transducers.
Note
Level could be measured in many different ways. Whether gravimetric as described, or with a submersible pressure sensor, float switch or pressure sensor ? WIKA gets the right sensor for each and every application. Do you want to buy the products? In our WIKA online-shop you will find some of our standard designs. Assuming you have any questions, your contact will gladly help you.
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