I have a normal strain gauge load cell with sensor capacity 500kg. I have four gauges following the rule of wheatstone bridge, two up two down. Many times in a load cell one gauge is damaged. Is there way I can complete the circuit with three gauges by applying any kind of resistance?
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You can add resistance in place of a damaged strain gauge, or use a half bridge of two gauges, BUT your cell will be far far far less effective - for practical purposes probably useless. A major reason for having 4 cells in a 2 + 2 arrangement is to provide a balanced output so that all that is seen are "difference voltages" due to gauge elements being placed in compression on one side and tension on the other. You can make a half active bridge with two gauges in one leg and two resistors in the other - this gives half the delta voltage compared with 4 cells BUT a major difference is that you lose thermal compensation. With 4 cells, when the host material is heated or cooled it affects both bridge halves the same (in a properly designed bridge) and has little or no effect. In a half bridge you have no temperature compensation at all. In the worst case temperature generated voltages can exceed the target strain generated voltage changes. |
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