[AVR] 4 Half bridge load cell wiring

[rochabg]

Hi!
I have this four half bridge load cells: https://www.ebay.com/itm/291121350051
I am trying to wire them to get best voltage output(voltage difference from balanced state)(not sure how to name this property), and i did some experiments with voltmeter and 5v supply. BTW i am making digital wheight scale.
Each load cell has three wires because is half bridge.
RED is output as you can see in the link
BLACK is positive excitation voltage input and
WHITE is negative excitation voltage input.
I tried two wiring options with two load cell forming full bridge:
1. -I connected black wires together with positive excitation input
- , white wires together with negative excitation input
- and measured output voltage between red wires.
in this option when preassure is applied on both cells bridge remains balanced, so it is not a solution. so I tried second option.

2. -I connected black and white wires on positive excitation input
- I connected remaining pair of black and white wires on negative excitation input
- and measured voltage between red wires.
In this option cells do not cancel each other, say both are constructive, so it seems like a solution?

Now I have two questions:
1. I didnt expect anything to change by combining black and white wires, so can somebody please explain internal disposition of this load cells half bridge? I mean if two strain gauges of one load cell are conected as a voltage divider as in the picture in the link what exactly has changed when i combined black and white wires? Is one of strain gauges inside of a cell a dummy one, the one that doesnt strech but just compensate temperature(this might be correct)?

2. Can I simply double the wiring with remaining two load cells, so that four load cell are used? So two pairs of second option wiring is present. And can I read output voltage of such wiring from serialy connected red wires two get double voltage output?

And one more question:
3 . LEts say second option is sufficient in regard of output voltage. But that is only two load cells(2*50kg=100kg(load cell rated mass)) and i need one on each corner of a box(box itself is ranging from 80 to 120 kgs) that i am tryig to weight(4*50kg=200kg(also rated)). So, can i replace two load cells with some springs, rubber or some other kind support for two corners in a such way that i do not overload two load cells. Obviously i am trying two spare in investment

I hope i was clear. Thanks!

 

[FvM]

Internal design of the load cell should be of course described by the vendor. Generally you can expect that both resistors are apllied opposite force, so one is stretched when the other is compressed. The intended combination of two half bridges with one supply reversed sounds reasonable.

It's common practice to make a parallel circuit of multiple same type load cells (same bridge resistance and sensitivity) that share a load. This decreases rather than increases the output voltage but gives best accuracy without needing additional amplifiers.

The assumption that all load cells get the same load is generally not justified. That's why multiple load cells (e.g. three or four) are used if no balancing mechanics is available. Of course you need to check your specific design.

 

[rochabg]

It's common practice to make a parallel circuit of multiple same type load cells (same bridge resistance and sensitivity) that share a load. This decreases rather than increases the output voltage but gives best accuracy without needing additional amplifiers.

We are talking about weathstone bridge here, Right? Can you please clarify this: "This decreases rather than increases the output voltage but gives best accuracy without needing additional amplifiers". I tought Amlifier is neceserry? So , how would i wire four half bridge load cells(from the link)? I found this



Is it ok?
I am sorry if I missed category with this thread!