A microprocessor based air pressure controller is discussed. The particular implementation was designed around an existing pressure measurement, and display unit. The unit is controlled by a 6809 microprocessor. It is shown that due to the many functions that the unit must perform and control, a microprocessor based system is a good choice. The controller is economical since it uses standard chips, yet it is very accurate since it uses state of the art pressure transducers. Experimental results and the user friendly interface will also be discussed. A commented listing of the controller software, and the circuit diagrams are appended. / Master of Science