I am interested in building an instrumented load cell to support Candy and Composite rocket motor characterization.There seems to be some amount of activity on the net - but when it comes down to it - not much posted and not a whole lot of follow through. Likely it's cumbersome ot post in useful detail and for similar reasons difficult to do more then jump in on highly targeted questions. So, for now, I feel largely on my own. I shall revisit the web-gods when I feel like I've got a half decent proposal worthy of comment.
I think 'professor Terry McCreary's Composite Motor Handbook details a complete load cell setup. I may have to afford his book. But then again, I believe I can pull this off, save a few $, and have fun in the process. Note that unless you're doing something odd you'll find the manufacturers application notes nearly if not totally sufficient to work up something that will work.
Paul Kelley has a nice A/D Converter Page. Richard Nakka has a nice site and in particular for this, now is working up a load cell page.
What is needed is a load cell, likely straing gauge based, an instrumentation amplifier, one or more channels of A/D conversion, and software for analysis.
I am currently planning on building a load cell following Richard Nakka's work.It uses some home or machine shop worked AL with some Omega strain gauges.
It seems like the TI INA125 is the most popular instrumentation amp. It has many nice attributes that make it a near single-chip solution with few supporting components. Features such as reasonable Vcc supply options; direct strain gauge bridge design; built in precision voltage references; etc. With few supporting components it should be able to directly drive an A/D converter. I believe it's the amp used in 'professor's book.Paul Kelley seems to be using the TI INA122 which appears to be a micropower version of the INA122.
I am looking to leverage Paul Kelley's A/D Converter work. It uses the TI TLC542. The TLV2556 is TI's suggested replacement for the TLC2543 (and is only $7). It is 11 channel and features direct serial output which is very nice.
Sensor Design PDF. Cached here.
INA122 Instrumentation amplifier. TI Site Product Page; App Notes. Data Sheet Cached.
INA125 Instrumentation amplifier. TI Site Product Page; App Notes. Data Sheet Cached.
TLC2543 12 bit, 11 channel A/D Converter. TI Site Product Page; App Notes. Data Sheet Cached.
TLV2556. TI Suggested upgrade to TLC2543. TI Site Product Page; App Notes; Data Sheet Cached.
Omega sells strain gauges, load cells, and has good technical references
Richard Nakka's Main Page and Strain Gauge Page
Paul Kelley's A/D Converter
'professor Terry McCreary's Composite Motor Handbook
The Art of Electronics, Art Baker