Figure F21. Schematic illustration of the MWD tool. Drilling fluids are constantly pumped down the drill string, and periodic closure of the MWD valve creates pressure pulses that can be detected on the rig floor.

Figure F21. Schematic illustration of the MWD tool. Drilling fluids are constantly pumped down the drill string, and periodic closure of the MWD valve creates pressure pulses that can be detected on the rig floor.