I am looking for a digital device that is able to measure the angle of a rotating device. It will be used to align rotating solar cells with the sun. These cells are attached to a flat panel, that is fixed in the center with an axis, so only circular movement is possible. The panel needs to rotate from East to West (approximately) to optimize energy production. The position of the sun can be calculated, but the position of the solar cells need to be measured. I tried to use a fluxgate compass first, but this device is not accurate enough and needs to much time to stabilize. So what I'm looking for is an alternative to measure the angle between the solar cells and the axis. Any suggestions? Thanks!