SOLVED: see: www.ortodoxism.ro/datasheets/analogdevices/259181025OP297_d.pdf

Hi,
I have three analog outputs from an accelerometer, (x, y, z axis)
What I would like to get is the amplitude of the resultant vector. (direction not necessesary)
Would like to keep everything analog.
We are measuring the impact of an offshore race boat on the water after a jump, so there is no need to be extremely accurate.
Signals are 1.65 V at rest, varying up and down in motion.

I would like to work with instrumentation opamps, since I know those best. (well, only thing I reasonably know....)

All help, links etc welcome.

Regards, Geert-Jan

 

The vector magnitude is the square root of the sum of the squares.
1. Square each of the signals
2. Sum the results with a three input summing amplifier
3. Take the square root of the result.

The best place to look for these circuits is Application Notes from National Semiconductor. Possibly Horrowitz and Hill