I neglected to mention that the MEMSIC sensors are less than 
  $10.

Probably they aren't interesting to the PSN, but if you 
wanted to instrument a high-rise or a bridge really cheap, 
they might be.

Doug

ChrisAtUpw@....... wrote:

> In a message dated 03/06/02, dcrice@............ writes:
> 
>     I saw some low-cost MEMS accelerometers at the Sensors Expo that
>     looked interesting as strong-motion sensors.
>     http://www.memsic.com/default.asp
> 
> 
> 
> Hi Doug,
> 
>       Looking through the data sheets, the minimum noise is 0.3 milli g 
> / root Hz, so at 10 Hz you would see about 1 milli g noise. The output 
> sensitivity is quite temperature dependant. They don't sound very exciting.
> 
>       The ADXL05 is obsolete and has been replaced by the ADXL105 at 225 
> micro g / root Hz. .
> 
> Quoting Larry's findings:-
> 
>       The main difference between the ADXL05 and the Kinemetrics FBA-23A 
> is the amount of background noise from the sensor itself. The ADXL05 
> sensor has about +/-3 mg of internal noise and FBA-23A has less than 1 mg.
> 
>       Looking at Kinemetrics literature, they quote noise levels of the 
> order of 1 micro g.
> 
>       I would not expect to see a great deal of improvement for the best 
> Memsic over the ADXL105. Maybe there is a difference in price?
> 
>       The 3022's are quoted as giving 1 micro V p-p noise for 8 to 20 mV 
> / g output to 50 Hz, which sounds about a factor of 10 better than the 
> ADXL105.
> 
>       Regards,
> 
>       Chris Chapman.


-- 
Doug Crice			 http://www.georadar.com
19623 Via Escuela Drive		      phone 408-867-3792
Saratoga, California  95070  USA	fax 408-867-4900

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