Dynamic pressure sensors are installed at each compression chamber to measure the performance of the compressor Access to the compression chamber is possible via a so-called indicator port. API compressors usually have these indicator ports. If this possibility is not given, there is still the option, for example, to modify the suction valves with a indicator kit. This involves replacing the center plate of the valve through a modified plate that has an opening in the center bolt area. This opening allows the pressure sensors access to the pressure chamber or compression chamber and thus measures the present pressure.