Building a Force Sensor: What You Need & Where to Buy

[sjaguar13]

I need to measure force and input the data into a computer. I found some force sensitive resistors, but they weren't capable of handling forces of several pounds. What I wish to build (if cheap enough) is something like this:
http://www.vernier.com/probes/probes.html?fp-bta&template=standard.html

Anyone know what is needed to build one, where do buy one that's cheaper, or is that the best I am going to be able to do?

 

[FredGarvin]

You're not going to find much cheaper than that. Most load gauges are strain gauge based. When you add in the electronics for that portion, plus the electronics for the output you're starting to get a bit higher cost. What are you willing to spend? There are some scales and hand held force transducers that output on a serial line. What exactly are you doing with it would be helpful to know.

 

[berkeman]

How about using a spring and a linear potentiometer? Choose the spring so that it stays linear for the forces that you want to measure (F=kx), and monitor the resistance of the wiper of the pot. You could even do a cheap RC thing if you don't have an easy way to read the resistance. Add a capacitor and drive an edge into the potentiometer+cap from the TX line of the serial port on your PC. Monitor how long it takes for the RX line to respond to the edge going through the RC lowpass circuit. You can probably calibrate the whole setup to be accurate to within a few percent...

If you have a simple analog I/O card in your PC, you could just measure the resistance or form a voltage divider to tell you the wiper position. Let us know what you come up with! -Mike-

 

[dlgoff]

I need to measure force and input the data into a computer. I found some force sensitive resistors, but they weren't capable of handling forces of several pounds. What I wish to build (if cheap enough) is something like this:
http://www.vernier.com/probes/probes.html?fp-bta&template=standard.html

Anyone know what is needed to build one, where do buy one that's cheaper, or is that the best I am going to be able to do?

How about buying a cheap digital bathroom scale and interface to its' electronics?

Regards

 

[dlgoff]

If your computer has a sound card you can input data with http://polly.phys.msu.su/~zeld/oscill.html.

 

[vgthoummany]

Can you use a torsion spring with a potentiometer to measure the force.d