Abstract: A rotating testing device can be connected to a base unit. A temperature sensor can also be connected to the base unit. The testing device has probe heads. The probe heads are immersed and rotated in the liquid concrete and the force required for rotation is measured in the base unit. Various concrete recipes are stored in a memory of the base unit. Data concerning the concrete are calculated by comparison with the force required to rotate the testing device with the force derived from a respective stored characteristic line and are read from a display field. A concrete recipe and specific measurements are selected by actuating keys which select the respective electronic processes in the base unit for measurement and comparison with stored characteristic data.