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Title: why the nominal resistance value of a strain gauge is 120 ohms? Post by: Fireman 23 on Oct 6, 2012 why the most common nominal resistance values of strain gauges are 120, 350, 700, 1000 ohms?
Some one told me that it is because of the nominal resistance of the first proposed strain gauge in american in 1938 is 120 ohms. so now all the strain gauges in world follow these values. but why? and why the gauge factor is 2? Title: why the nominal resistance value of a strain gauge is 120 ohms? Post by: smrogers on Oct 6, 2012 Because that is what they originally built their resistances to be. There is no reason why it couldn't be anything else.
Title: why the nominal resistance value of a strain gauge is 120 ohms? Post by: otter1202 on Oct 6, 2012 Probably the makers of strain gauge instruments standardized on using a 120 ohm gauge a long time ago, and now that is the value that works well with standardized instruments. This effect is often called "lockin" and occurs in many technical fields. 50 ohm RF coaxial cable, 300 ohm twin TV cable, VHS videotape, the Iphone etc.
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