Integrated Scientific Resources Uses Optimization to Compensate Strain Gage Bridges
Strain measurements often use a Wheatstone bridge consisting of four strain gages. Such bridges require compensation resistors in order to maintain a minimal output when under zero strain over the nominal temperature range of the bridge.
Using optimization methods, Integrated scientific resources developed and implemented an algorithm for selecting the compensating resistances to achieve relative imbalance better than 0.05% over the range of the bridge operating temperatures.
The algorithm takes accurate measurements of gage resistances at cold, ambient and hot temperatures. Using this set of 12 resistances obtained under zero strain, the algorithm finds the parallel and series resistors required for compensation.
The software is undergoing rigorous testing and validation by Integrated Scientific Resources customer and is slated for full production release within a few weeks.
On the drawing boards are a set of planned improved such as selecting the compensation values from a predefined set of standard resistor values thus bringing the calculated outcome closer to what is achievable on the production floor.
Figure 1. Shows a screen capture of the application after zero span compensation and full span sensitivity calculations.
Figure 2 shows the slot panel populated with three bridges.