Why are Multiple Load Cells Used in Weighing Systems?

One reason is to enable you to measure the Center of Pressure.

Another reason is that it can be difficult to balance the mass to be weighed evenly on a single loadcell (causing measurement errors or even mechanical loadcell damage).

3 or 4 LCs platform may sustain to greater load no matter where (and how) weight is put on platform, but there could be some problems connected to its adjustment due to the mech system is statically undetermined.

There's an advanced design with so-called "single point" weighing system using only one LC in. But application of this is restricted due to known problems (a risk of damage and errors caused "out of center loading" include).

BTW why didn't you ask of "one-leg" chair design? At the time I've seen one at my friend's home who's sister learned play on piano.

Think about it. If you had one load cell you would need some way of balancing the load. So would two. Three is a little better and four seems to be what they use to weight products on rectangular platforms

With 4 on a scale, each one can to be smaller and the weight can be summed, and there is never a balance problem.

the most common place I see single load cells is when they are on a crane cable or magnet crane cable, as you can weigh a load quite easily on a sling like that.

yes, I have seen the small scales with a single load cell that take a lever mechanism and bring it to a single point load cell.A friend of mine owns a scrap yard and has a 5 tonne drive on scale that has 4 load cells and a wire harness. It is about 4 inches high, flat on the ground. It might be that scales that have space for the lever mechanism can use a single cell and the places where you are dimensionally limited, you use multipoint cells?

The load is never placed on the center of the platform. The scale adds up what it reads to give you a single number.

Follow the link

to an example of single point load cell application

not only a single cell it is on a conveyor

Even though its a single point there are actually 4 cells set up as a bridge to improve accuracy.

I wonder if the single point application at the scrap yard is similar?

The scales I have seen at the grocery check out use a similar configuration

the 4 cells with in the unit are oriented in different ways to give you the accuracy, uncentered loads are automatically compensated for in this manner

A flat bed 4 cell unit is much simpler mechanically, and less troublesome to maintain.A single cell unit has a complicated pivoting and load-sharing construction, and all pivot points can incur wear, affecting accuracy.

A single cable type can work with one load cell, because the load is automatically centered by the cable itself.

I have already seen some pretty near to good answers here, but the point is that accuracy is far greater with multiple cells, and the cost is a lot less. One single cell to carry ,say, 100 tons will be large and cumbersome and difficult to install and secure. Whereas 4 units of 25 t each will do the same job with greater accuracy and as a bonus a load can be placed anywhere on the table. Suspended loads operate fine from a single cell, but even here multiple cells will work better, like square bins hanging from its corners.

If you have one live load cell and two dummy load cell for bin weighing, it will not always give accurate reading. Consider the case of solid material in a bin. If the material filling is uneven (at one side higher level then other side) in the bin, the load is not evenly distributed evenly to all three load cell. This may generate the error. Accuracy is obtained only if bin is filled uniformly. With two live load cells and one or two dummy loadcells, situation can be improved. But maximum accuracy can be achieved only if all three or four load cells are live. I hope I have make you clear. -Sandip Patel

Consider the mechanical difficulty of balancing an inverted cone on a single loadcell, then. The arrangement is metastable, any disturbing force making the cone topple.