The apparatus has a pneumatic controller, which controls the pressure in a gas conduit in dependence on the pressure in an air conduit. The light receiving element 12 separately receives reflected main beams used to read information from an optical disc and reflected sub-beams used for a tracking operation with different ones of the light receiving regions. The self-cleaning filter has a purge output, which may spray the pre-filter to substantially remove particles from the pre-filter for collection in the containment tank. As the tube is exposed to a differential pressure, said tube unwinds, thereby creating a rotary motion that is proportional and linear to said differential pressure sensor, thereby providing an indication of pressure within a downhole environment. This can be easily implemented on most types of powered screwdrivers including the most common device used for screw insertion on a construction job site, the cordless drilldriver.