I've been tasked to design a circuit which measures the peak impact force of a crimping press on a terminal. I am using a load cell under the press as a sensor. The load cell outputs 20mV (differential) at full scale (4000 kg force). The impact is quite fast - an entire crimp is over in about 20-30 ms!
The approach I've come up with is as follows: feed the load cell's differential output to an instrumentation amplifier (gain ~ 200) which in turns a peak detector and that in turn is fed to a 10 bit ADC on my AVR. I've tried this approach and while it works quite well it's not repeatable enough. The noise in the system makes repeatable measurements difficult. Please note: I've only tried this on a veroboard and haven't yet tried it out on a PCB. I intend to do that soon.
The 2nd method which occurred to me was that I could use a differential ADC with built-in gain of, say, 200x+ and directly obtain the result that way. The only downside is that I'm not reading the peak value - but I can always do some processing and find the peak value. Is the second approach inherently better?
I am also open to other ideas. The goal is just to measure the peak force and then compare that with a programmed range in the MCU to see if the force was too high or low.