Magnetic Field Strain Gages
Intense, time-varying electromagnetic fields with steep gradients in field strength can cause troublesome noise in strain gage circuits. In severe magnetic environments, with low signal levels, the noise amplitude may be several times larger than the strain signal from the gage. Micro-Measurements H-Series noninductive strain gages have been specially designed to minimize noise pickup in the gage grid due to electromagnetic fields. H-Series strain gages consist of two identical grids, with one stacked directly above and insulated from, the other. The upper and lower grid elements are connected in series so that current flows in opposite directions through the two grids. With this arrangement, noise voltages induced in the grid tend to be self-cancelling. The counter-current principle employed in H-Series gages is particularly effective against magnetic field gradients parallel to the test surface. H-Series strain gages have been used very successfully in fusion research applications and similar environments with flux densities to 50,000 gauss.