AE = ED; AB = DC; AD = BC
FC is longer than BF
ABCD: parallelogram
Move orange slider to make the pink beam horizontal. Final position of the slider shows the weight of object being weighed (in brown).
Q = G * EG / (2*(AE – BF))
Q: weight of the brown object.
G: weight of the orange counterbalance
(AE – BF) can be very small so Q can be very large while G and EG are kept the same of the ordinary steelyard.