http://www.omega.com also has some SGA for around the same $300 price. And google turns up many other turn key solutions. http://www.google.ca/search?hl=en&q=%22strain+gage+amplifiers%22+multi+channel&meta= Prices vary depending on features (# channels, frequency response, stability specs,) http://www.grasstechnologies.com/products/amplifiers/p122.html Grass has been doing this for decades so they know what they're doing. Well built. Found this helpful app note while looking. http://www.iotech.com/catalog/techtip/TechTip_60602.pdf There are A/D cards that are made specifically for strain gage use. http://www.iotech.com/strain.html http://www.iotech.com/catalog/daq/strainbook.html 8 channels, 16bit 1Mhz SGA+ A/D for ethernet. $6k Don't forget that at the voltages you are measuring that thermocouple effects can be significant sources of error. Robert Bill Clawson wrote: > I looked at the national instruments website and their > units start at around $300. If you're willing to > plunk down the money, you may want to start there. > Otherwise, there are instrumentation amplifier ICs > from places like Analog Devices, and it seems to me > that coming up with a custom circuit might not be all > that hard, albeit I haven't found one on the web just > yet. > > Bill > > --- Denny Esterline wrote: > > >>A colleague of mine recently had a minor car >>accident, he'll recover- but >>I've been asked to pick up one of his projects while >>he's out. >> >>I have a three axis force transducer to install in a >>ELD wind tunnel. Three >>separate four-arm strain bridges ~900 ohms. With the >>recommended 10 volt >>excitation I see about +-7mV at full load. The DAQ >>hardware that accompanied >>this is a NI USB9215A with +-10 volt range and 16 >>bit resolution. (I'll save >>you the math - 305 uV :-) >> >>Clearly I need better resolution. >> >>Always looking to heat up my soldering iron, my >>first thought was to lash up >>a three channel amplifier unit with something like >>TIs INA129. Then I came >>to my senses. This is a reasonably well funded >>one-off project, custom >>hardware probably isn't the best choice. >> >>So, does anyone have recommendations for a more >>suitable DAQ unit or a >>suitable amplifier unit to tie these together? -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist