24 September 2011

App Note 43 part 3

Just a quick post to finish up App Note 43: This note ends with five appendices, two of them with guest authors. In Appendix A, Jim writes a little about the history and construction of strain gauges, and introduces the first guest authors from Motorola Semiconductor (since spun off into ON Semiconductor and Freescale Semiconductor), who write about semiconductor-based strain gauges, which they spell "gage" (Jim explains the alternative spelling in the first footnote on page AN43-36). I wonder if this foray into semiconductor gauges was part of the original impetus of this app note?

Appendix B discusses historical bridge-readout techniques, starting with nineteenth-century galvanometers, and continuing up through modern chopper-stabilized amplifiers and analog-to-digital converters. Again, he gives unwarranted credit to Lee DeForest, which is disappointing. Note the captions in Figures B1 and B2, "Courtesy the J.M. Williams Collection."

Appendix C (briefly) discusses Bill Hewlett's oscillator design and includes the schematic (Figure C2) from his Stanford thesis.

Appendix D presents some theory behind distortion measurements, and is written by guest author Bruce Hofer. There is some good discussion here. Unfortunately, he starts the appendix by defining "linear distortion" and "nonlinear distortion", the former of which I consider a oxymoron.

Appendix E briefly mentions some cabling and filtering considerations for bridge circuits, and the final page is another of his famous cartoons, this one starring the Golden Gate Bridge.

Best quote (page AN43-42): "The Hewlett-Packard Company and light bulbs have had a long and successful association."


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