Balanzas

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Re: HOW DOES A BELT SCALE WORKS?
08/25/2008 2:11 PM

Principle of operation is very simple

In a word one of belt conveyor idlers' is resting on load cell (weigh sensor),therefore signal from its sensor Uq does correspond to mass of bulk material/per idler's span q measured in [kg/m],[p/f]. I.e.

Uq=k1*q, k1 - transfer coeff.

There is as wellspeedometer either if you wish belt's speed sensor which produce signal Uv corresponding to speed of traveled belt V measured in [m/s],[f/s] i.e.

Uv=k2*V.

When we multiply these twosignals we shall get

UQ=k1*k2*q*V=k*q*V, [kg/s] either [p/s].

i.e. UQ is corresponding to instantaneous flowrate. For getting total result of how much of bulk material had beenpassed through conveyor we must integrate results by means of integrator[totalizer], i.e.

Q=k∫UQdt, [kg] or [ton]

Either for simplicity

Q=q*v*t.

As for conveyors we haveflowrate measured in tons per hour. Last expression could be written as

Q=3.6*q*v*t,

There were explained principle of simplest belt scales (belt weigher) which using analoguetechnique of measurement.

First BW had been appearing at 1908 and its been designed as completely mechanical. There were further developing of BW based on electromechanic,electric, hydraulic, analogue electronic, digital electronic and microcontroller basis.

Main advantages of BW are --- relatively low cost, ease for installing everywhere you need.Main disadvantages --- its very very unstable in terms of accuracy, here's as well impossibility for most cases to perform properly adjustment tests.

On my opinion to call thisdevice "a scale" is very controversial practic, so I do prefer to call its a weigher.

How one idler BW looks you could see here

Block Diagram of uC implementation

Hope it helps
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