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Building a vibration sensor

Building a vibration sensor

Building a vibration sensor

(OP)
I'm building an acceleration sensor for a project with low g's.  (.05<g<1.0 max g = 2.0) I've researched several sensors on the web and have selected a sensor with a sensitivity of 120 pV/g.  

My understanding is there is a known mass that reacts to the vibration.  This reaction is output as a certain voltage.  What I am attempting to do is interface my accelerometer with a circuit board.  

Would anybody know how I would do this?  I would like to make a direct connection to the ADC without using an amplifier circuit.  With this in mind, what would be the best way to do this? If I go as high as 2.0g's would you know how I could limit this voltage to keep it from overloading the processor?  

Any help would be greatly appreciated.

RE: Building a vibration sensor

If you don't want to amplify the signal then I think your asking for trouble with pico volt signals. Noise is often much larger than this in magnitude. Are you planning on using a filter? Also, 240 pV will not hurt your processor at all. You might consider putting  a zener diode in on the input to the processor to protect it if you end up with a direct connection.

RE: Building a vibration sensor

Which sensor are you using ?  Reason I ask is that there are several interface methods available from these types of devices.

For example, I'm familiar with the ADXL202 G-sensors

http://products.analog.com/products/info.asp?product=ADXL202

Also, here's a nice little project for an automotive G sensor using the ADXL202.

http://www.ghg.net/stuart/accelerometer/accelerometer.html

The ADXL202 can interface to the microcontroller in two ways.  One is using a pulse-width-modulated signal, where the G force is represented by the ratio of the pulse duty cycle to the pulse width.  No voltage levels to worry about.  If you want to talk directly to an A/D, then you can pull the actual analog signal from before the filter caps and measure it yourself.

Search google for adxl202 - there are lots of hits.

Dean.

RE: Building a vibration sensor

I am suspicious of the picovolt ref. That is a tiny 240*10^-12 volt, way down in thermal noise and too low for common interfacing.

channey99 - Hi. Good refs on the devices.
A little OT for the thread, but I stumbled onto a link with some Toyota interface details. It might be useful to you for your datalogger proj, in case you don't have it. This is the top page:
http://www.autoshop101.com/autoshop28.html

ron

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