Temperature effects on strain gages used on aerospace nickel hydrogen batteries

One of the advantages of aerospace nickel hydrogen cells is the ability to determine the state of charge of the cells by measuring the internal cell pressure. The internal cell pressure is also proportional to the induced strain in the cell pressure vessel wall. A common technique is to use bonded foil strain gages in a Wheatstone bridge configuration to measure the induced strain. If bonded foil strain gages are used to measure the induced strain, several temperature induced errors result. This research focuses on the effects of temperature on the resistance associated with the strain gages, the ladder resistors and the copper connecting wires. Several computer models are used to compare the temperature effects on the Wheatstone bridge with the ideal Wheatstone bridge output.