Can I make an force sensor out of my accelerometer sensor so that I can calculate the force being applied on any object (force function)?
Hello Suman,
I see that you have also another question of similar topic, about a bridge and accelerometers. I'll try to give you some hints:
- what do you need the force calculation for?
- recall that F = m * a (so, if you would know "m" then you should be able to calculate F). However this equation would only apply for an ideal free moving object. In the case you consider a building, like a bridge, then the measured accelerations represent something that is FOR SURE connected with some impulse or force applied on the bridge, with a connected transfer of energy, however the system is too complex to infer such a simplistic equation.
Suggestion: ask a building or civil or other type of engineer or expert in building / structure, possibly with a background on dynamics and not only static calculations, in order to get a better understanding of the "meaning of accelerations" in your particular case of study.
Daniel.
Hi Suman, We have well known that an accelerometer is a device that measures proper acceleration. If you obtain the acceleration value of a measured object and know the mass of object, so you can use the formula F = m.a to calculate force that works on the object.
Thats fine.Actually my motto is to calculate the FRF-Frequecy response function of a bridge.I have accelerometers but I don't have any force sensor that gives the force applied by the moving train on the bridge.
Then how do I calculate the FRF for my bridge??
Hi Suman,
Indeed most MEMS accelerometers are based on a load attached to a spring, so the sensor is already measuring a force (and is calibrated as 1g in static conditions). The relationship between force and acceleration is just a multiplication for the mass quantity, so the frequency response is really just the same.
On the other hand, I had experience in measuring the freq. response of structures using sensors (MEMS and fiber optic). If you want to have the exact response, this also depends on how the energy is transferred from the structure to the sensor, so the package for example can provide an alteration particularly if you consider a limited range of frequencies (usually 0-100 Hz for civil engineering). So it's probably this function that requires the hardest calibration.
For the measurement, a possibility is to calibrate the unit with a known object, that gets stimulated e.g. using a shaker. We did it, with a carbon fiber panel mounted to a shaker that could apply several types of mechanical stimuli, and we were able to measure (just by doing the FFT of acceleration) the spectral profile, which should have a resonance peak + harmonics.
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