as RDS said, look at load cells.
most all load cells are mv/volt excitation, so you will need an amplifier.
you can buy them 0-10v or 4-20ma.
CAUTION - this is from experience.
what is your application?
I say that because load cells are subject to destruction from load shock.
applying a load to a load cell is one thing, applying a sudden grip load is another story.
sudden application of a force to the load cell will result in an impact load of 6-10 times what the load sees after it settles (2-3 seconds later).
for example, picking up a 25 lb weight using an air cylinder even 1 inch at what I considered a slow rate caused the load cell to fail after a month.
we had to use a 250 lb load cell. we soon learned to increase our load cell capacity by a factor of 6 to 10.
james