scale and XY coordinates with load cells

Community Projects
1

Hello.

i am trying to build a scale and XY coordinates with load cells.

i have: 1 big plate (2X1 meters) and 4 load cells (each is max 200kg).

the 4 load cells are connected to the ground, each of the them separately with bolt from the bottom.

the big plate has 4 bolts, 1 in each corner.

i am putting the plate so the bolts are placed on the load cell where.

All those connections are made right and there are not the problem.

now i want to scale something on the plate and to know the center of pressure of it.

lets start with the scale.

I dont know the weight of the plate and i cant scale it somewhere else. but it sure somewhere around 80-110 kg

before i placed the plate i made some tests.

i individually loaded each load-cell with weight the i know. and made a graph of it, for each load-cell

y=a*x+b

where x is the mili-volt value that i get from the load cell with amplifier. and Y is the weight that was loaded.

now i placed the plate and got all 4 reads from the load cell. with the Equations i found i just summed all

Y1=y1 + y2 + y3 +y4

then i stood on the plate and measured again all 4 reads. and summed it too:

Y2=y1 + y2 + y3 + +y4

so Y2-Y1 = suppose to be my weight.

But unfortionatly its not working. i weight around 80kg and i get Y2-Y1~300 kg

please help me find what the problem.

2

Your general approach seems correct, but if you want help, show us the individual cell calibration data (test loads and measurements, the graphs would be good too), and then the results of both overall measurements.