MEMS high resolution 4-20 mA current sensor for industrial I/O applications

An isolated MEMS-based 4-20 mA current sensor device has been developed for industrial automation applications. This device consists of a current carrying suspension that is electrically isolated, yet mechanically coupled to a bank of capacitive comb fingers. Under the presence of a magnetic field, the sense current produces a Lorentz force that laterally deflects the device. The deflection is capacitively detected. Using various flexure designs to tune the sensitivity and current capacity, this device can be made highly linear with a sensitivity of 0.25 /spl mu/A.