PH is measured by a combined, sterilizable ph electrode with incorporated temperature sensor. Thanks to the multiple variopin plug it can be sterilized without any protection. The two-point calibration of the electrode is semiautomatic. The ph value has an automatic temperature correction. The addition of acid or base is controlled by a microprocessor. The flow rate of the peristaltic pumps preciflow, multiflow, hiflow or maxiflow is varied between 0 to 100%, which makes the ph control smoother than with the common on/off switching of fixed speed pumps. The unique pump flow integrator (option) when coupled to the pump enables monitoring of the pump’s activity during the process. This yields precise kinetic data concerning the culture state and activity.