> Question was brought up, and perhaps someone has an answer.
>
> The problem to solve is to be able to repeatable and reliably  
> measure a weight of a range of 35lbs to 150lbs using some sort of  
> flat & flexible surface.  I've used load cells before but they are  
> too bulky and expensive.  Ideally he wants this to be portable and  
> flexible so some sort of resistive network maybe?  The range can  
> also be divided up...say 35 to 65, 65 to 95, etc...one model does  
> not need to cover the entire range.  Also it does not need to be  
> accurate to the pound..can be +/- 2 to 4 pounds.  The micro would  
> measure the output of the sensor, and do a lookup table or something  
> based on what is coming in.  Its more of a go/no go type application.
>
> Any thoughts?
>

Apply the force to a metal strip that will flex with respect to  
another conductor.
measure the change in capacitance.
There are a gazillion ways to measure capacitance.  There are ICs that  
measure capacitance.
        http://www.discovercircuits.com/S/s-capacitance.htm
        http://www.analog.com/en/analog-to-digital-converters/capacitance-to-digital-converters/ad7150/products/product.html

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