FSR pro’s and con’s:
FSRs are just resistors, so they are easy to work into circuits, and sometimes don’t require any support circuitry. They are also relatively inexpensive and readily available, even Digikey has started carrying the Interlink FSRs. But, unfortunately, that is where the pro’s end. The main drawback to FSRs is a result of its central component – the spongey resistive material in the middle. Just like a sponge, it takes a while to re-inflate after its been compressed. And worse yet, this re-inflation time is a function of how long and how hard you pressed on it. After you release, the FSR value will come back to 95% of its initial value almost instantly, and then drift that final 5% over the next 10 seconds.
The inner material is also very sensitive to how it is pressed. It has a non-linear pressure response which varies with time, temperature, humidity, and even between parts of the same production batch. This makes the FSR a poor choice where accuracy and repeatability are a concern, especially across many units. Fortunately, a lot of musical applications have a human in the feedback loop who is able to just press harder or softer to get the desired effect, making this inaccuracy of less concern.
Finally, FSRs can also be very fragile. They are made of thin, laminated plastics, and are frequently placed under high forces.
Which FSR should I use?
The main two manufacturers of FSR sensors are Interlink and FlexiForce. Interlink FSRs come in a wide range of shapes, are relatively inexpensive, and fairly robust. On the downside, they vary greatly between units, have a lot of resistance drift over time, and are a bit slow to respond. The FlexiForce sensors, on the other hand, tend to be more accurate and repeatable, but are more expensive and fragile. In applications where exact forces don’t need to be measured, the Interlink products will probably serve you best. For more repeatable results, the FlexiForce sensors will be better (as they rely on the piezoresistive effect). But, if you really need consistent results, an FSR isn’t the best choice, and a load-cell or strain guage should be used.
more details at http://www.openmusiclabs.com/learning/sensors/fsr/
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