Two Wheatstone bridges values

My dilemma at the moment is that I have four 50Kg loadcells from sparkfun and I will be wiring them into two separate Wheatstone bridges.

First question is if two 50Kg sensors are in one bridge and both have a 50Kg mass on top will the resulting value be 100kg?

Second question, if I have two bridges one is measuring 48Kg and the other is measuring 22Kg will the total be 70Kg?

Load cells are usually (not always) Wheatstone bridges with four wires to them. Applying a force causes a tiny change in voltage across the bridge.

One loadcell is sufficient to measure a load. With 4 cells you can measure 4 loads independently, but I doubt that this is what you want to do?

Oh, I did not know one was sufficient. But if two are together in a Wheatstone bridge is the total mass it can measure doubled? (2x50Kg sensors = Total mass of 100Kg?)

Tidsuo:
Oh, I did not know one was sufficient. But if two are together in a Wheatstone bridge is the total mass it can measure doubled? (2x50Kg sensors = Total mass of 100Kg?)

If you want to measure 100kg with a 50kg load cell you could use a mechanical lever with 2:1 ratio.

Load cells are not single variable resistors.

Tidsuo:
Oh, I did not know one was sufficient. But if two are together in a Wheatstone bridge is the total mass it can measure doubled? (2x50Kg sensors = Total mass of 100Kg?)

This works only when the load is distributed evenly onto both load cells - a mechanical challenge. Otherwise one of the cells may be overloaded.

Hi,
You regard each load cell as a separate measuring input.

So if you have four load cells ,one at each corner holding your object off the ground, then you take the mass reading from each unit and add them together.

Its called the principle of superposition.

You cannot gang the cells together electrically and get decent results.
If your object is 100kg and each cell is rated at 50kg then you can measure the mass, BUT you have to make sure that the mass is distributed in the object so that no corner is over 50kg.

What is the application?

Tom..... :slight_smile: