How do they measure Lbs of Thrust?

Question

Especially concerning Jet Engine, what type of measuring device do they use, or is there another method.

Answer 1

I'm guessing a little bit here... but they probably use load cells.  You can look up how load cells work but the basic idea is that they use strain guages that change (resistence I believe) in response to strain in a piece of metal.  That's what we use in measuring the thrust in rocket engine testing.

Answer 2

Its not measured  but calculated. You never really know the thrust it produces from the cocpit. What is measured is engine pressure ratio, EPR. This is the ratio of the ram presssure entering the intake vs. the exhaust pressure leaving the tailpipe. The higher  the EPR  reading the greater the thrust.