Position: This article is about the shortcomings and other problems of belt scales .
There are many of web-sites where've been issued whether detailed or not so detailed recommendations how properly to use belt scales (BS), how to install, how to test, choose when anyone wants them applied to for any kind of business. Unfortunately, there are not practically a comparable amount of articles, with detailed explanations why it should be done this or that way and how belt scale gets used to treat us back :).
At the beginning of 20s century, approximately at the same time when first cars had began their invasion on Earth the planet, first samples of belt scales had been appearing on plant's sites. Needless to say that first belt scales have had the same embodiment level as a firsts cars. Belt scales were unwieldy mechanical constructions being so unreliable as measuring instrument. But nevertheless it was incredibly disruptive innovation for that time's industrial production. Belt scales regardless known shortcomings were positioned beyond the competition and had occupied unique niche. Why a niche!? The virgin field a whole! No one rival measuring instrument neither static platform scale nor a truck or hover one could compete with such a low-cost and compact device as belt scale had been. That device might be installed in any place for measuring of conveyors’ flowrate in dynamic.
What is a modern car industry today? Isn't it a rhetoric question? Contemporary vehicle is representing a personified perfection, which has absorbed in the very advanced measures achievements of all technologies from new materials to IT.
As for belt scale, we, unfortunately, must conclude that inspite of applied the same kind of newest manufacturing technologies and a palpable progress in its performances, that progress doesn't look such a significant and stunning having been compared to not only car industry but to counterpart types of scales. As instance truck scale now can be made in handle-mobility embodiment possessing competitive low price.
Why it goes so? There is a handful of reasons. For aforementioned advantages of belt scale over of its history there had been forgiven obvious shortcomings that's been pretty acknowledged by all specialists. Things were going so at past and are remaining at the same place up to now:
- short-term durability period;
- weighing accuracy is depended on a lot of uncontrollable adversely affecting factors;
- only a few number of belt scales in restricted special conditions could be used as an instrument for legal-trade operations.
- most part of installed belt scales had the accuracy mostly appeared out of 1-2% or even worse.
These shortcomings looks paradoxically. How could some device being called as “ the scale” not be used as means for legal-trade operations?
Despite grown investments there had not been noted adequate responses in improving of metrological characteristics wherever you might see in advertising newsletters and booklets devoted to the belt scales. All well-known belt scale makers have a similar set of so similarly looking designs refelecting the same conceptual decisions. It does not look like real development but mutation.
It seems everybody all around had decided that problem of belt scale's accuracy had been already resolved (or will never be solved out ever) and keep reproducing last realization of belt scale design.
I think it's reflected even in OIML R-50 and other sources where belt scale have been renamed as belt weigher. Needles to explain that notion "the scale" has much more higher status than "the weigher". Term the scale implies that it's a measuring instrument for legal-trade operation as default. Isn't it?
I suppose the term "the weigher" has been "invented" for some smoothing out the contradiction between what we're waiting from device which is initially been called as "the scale" and what we've got in a real life. For the best understanding let imagine common situation when you’re treating a weigh of any thing like bags, basket of fruits, glass of water and so on by the means of your own hand(s). You treat it with help of your hand by lifting its up and down and you can even conclude that this item is rather heavier or lighter than another one. But it is not the instrumental measurement, as we can't make exact evaluation represented in scored mass units. Most part of installed belt scales/weighers just does the same.
Therefore we must conclude that all devices being released by manufactures are just belt weighers but only fewer of them deserved be classified as scales afterwards. It may be formulated either as “belt weigher or belt scale” problem or “BW-BS” problem. I am sure that I am not the first one who has realized this.
Surfing over the web some four years back I’d come across a stunning me article written by BobMalone (unfortunately I found this link not works, so I'll try to find where it placed now) where author so honestly and exactly had formulated "belt weigher-or-belt scale" problem. It was first inward “jolt” inside in my at the time pretty “hazed” intentions to create BW-site.
Bob Malone had made quite a pessimistic conclusion about applying BS as a truth measuring instrument. For so long I couldn't realize what touched me there. Even being not so experienced in English I could appreciate the lightness of his writing skill with a good bit of a good humor. But it was something else that I could realize far later. This belt scale was an incredible clearly and honestly formulated a real multi-field problem.