Compressors with a power source whose speed is controlled electronically provide a great opportunity to keep the compressed air constant within a very tight pressure range. A frequency converter, which regulates the speed on a conventional induction motor, is an example of such a solution. The compressor's capacity can be adapted to the precise air requirement by continuously and accurately measuring the system pressure and then allowing the pressure signals to control the motor's frequency converter and, consequently, the motor's speed. The pressure within the system can be kept within ± 0.1 bar.