acceleration sensing unit

I am designing a 3 axis acceleration sensing unit that is to output data for variuos yaw, pitch and roll with a known horizontal sway as input . This is an underwater application.

roms said:

When connecting up an 3 axis accelerometer to a circuit how do you get to store raw data on your system if it has to be underwater?

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Seal it in a water proof (and pressure proof) container, and read the data out afterwards - or via a wireless link.

With gyros and accelerometers outputing at the same time how can you distinguish outputs that were generated simultaneosly before storing them

roms said:

With gyros and accelerometers outputing at the same time how can you distinguish outputs that were generated simultaneosly before storing them

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Sorry?, don't see the problem?. Read them sequentially as normal.

how is it possible to pass an input from an integrator which is a ramp into an ADC and still get a digital output

Nigel Goodwin said:

Seal it in a water proof (and pressure proof) container, and read the data out afterwards - or via a wireless link.

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Sorry Nigel but radio does not work underwater.

JimB

JimB said:

Sorry Nigel but radio does not work underwater.

JimB

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I (very) carefully didn't say 'radio', I said 'wireless', which is a completely different thing!.

You might also like to inform the Navy that their radio links to submarines don't work as well? - it's just a question of what frequency you use.

Nigel Goodwin said:

I (very) carefully didn't say 'radio', I said 'wireless', which is a completely different thing!.

You might also like to inform the Navy that their radio links to submarines don't work as well? - it's just a question of what frequency you use.

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OK, I will give you the bit about "wireless" not being the same as "radio", but lets consider a few other options.

Optical, could modulate a light beam but the range would be limited (at the moment we dont know the range the OP requires).

Acoustic, tends to be limited to low frequencies and hence data rates.

Radio, generally does not work.
OK so what about submarines?
Submarines either use a floating wire or a tethered buoy with an antenna if they are to remain submerged.
It is possible for the submarine to receive very low frequency radio signals (10 to 20khz) while submerged, but the shore station has to use MASSIVE antenna systems and MEGAWATTS of power to make a usable signal for the submarine.

Have a look here:

for some useful snippets.

JimB

roms said:

how is it possible to pass an input from an integrator which is a ramp into an ADC and still get a digital output

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Not sure what you're saying. Most accelerometers have a DC voltage output proportional to the applied G-force. If you want to do integration do it digitally inside a microcontroller. You're putting this on a microcontroller, right?

BTW, determing location (double integration) or speed (single integration) from an accelerometer is often impractical. There are too many errors which build up over time to give a meaningful result.