At 12:14 PM 8/16/99 +1200, you wrote: >Hi, > >I'm working on a new project that will be using 4 load cells to >measure the weight of a piece of machinery during operation. I have seen this done in a number of applications. Key is to get really good signal conditioning on each load cell, then electronically add the outputs to a single sum to feed the ADC. Suggest Burr Brown INA118's (or 2128's for duals)--about the best out there. For 12-bit systems the AD627 is a good low cost option. Use an Analog Devices REF19x series regulator as the excitation supply. Then a really good low drift op-amp for the summing stage. The radio shack notebooks have some simple circuits that work well. You can add shunt calibration and zero by putting a mux in front of the ADC, and using optically isolated relays (Aromat AQV212S is what we use) to switch calibration resistors across legs of the bridge. Remember the shunt cal values are ADDITIVE to whatever signal is present, and assume the cell in unloaded and in a zero state to provide a true second point. Vishay/MicroMeasurements group has some really good app-notes out on the topic. Luck, Kelly **************************************************************************** ******** All legitimate attachments to this email will be clearly identified in the text. William K. Borsum, P.E. OEM Dataloggers and Instrumentation Systems &