Abstract: The present disclosure is directed to a mud metering tank monitoring system for use with an oil well drilling derrick having a sheave on the crown block and a bottom pulley forming a block and tackle arrangement with a cable supporting a traveling block adapted to be attached at one end to a pipe string for raising and lowering the string in a drill casing by a prime mover the other end of said cable being a dead line and having a weight indicator connected thereto. The tank has a mud pump and a fluid connection between the tank and the drill casing. Pipe string counting means is connected to be driven by the sheave in the crown block and to indicate pipe stands lowered into and removed from the drill casing only when a pipe string is being carried by the traveling block. A pair of vertically spaced apart mud sensors are positioned in the mud metering tank, and a computer panel is connected to receive input signals from the pipe string counters and mud sensors.