Measured Impeller Power in Watt

Improved cultivation with measured data

In order to calculate Power Number's one need preferably accurate data for “rotor/impeller power” in Watt. For larger system (>500 liter) the fixed speed electrical motor efficiency and internal friction in motor and gear box is well known. For smaller systems with variable conditions, less than 50 liter media volume its very difficult to obtain reliable data for Watt lost to the media by the rotor/impeller. Check out this page about Power Number calculation.

In order to measure accurate “rotor/impeller power” in Watt for smaller systems Stobbe Group have created the Perseus Drive Unit.

Perseus Drive Unit with servo motor mounted on MST driving a SUB and servo motor on a SUB with HPD.

The mechanics, electronics and software are matched together so the Perseus can measure the power in Watts required to perform the agitation. Independent of the combined internal system resistance forces (friction), the liquid viscosity, liquid density, the type and size of impeller – Perseus will give accurate measured Watt number with reference to variable RPM.

So, skip the guessing and measure online / real world Watt numbers and then calculate the Power Number. Perseus is available from sister company -

We are working on testing a range of CerCell impellers/turbines and establish accurate results. You are welcome to participate in our work.


“Power Input Measurements in Stirred Bioreactors at Laboratory Scale”, Stephen Kaiser Finesse USA, Soeren Werner ZHAW, Switzerland – 2016 -