PURPOSE: To achieve an unmanned operation of a device and at the same time monitor viscosity essentially continuously by controlling a pump automatically by a sequencer and feeding a sample to a measurement bath repeatedly continuously without any human operation.

CONSTITUTION: A substance to be measured, for example a motor oil, is sent to a pipeline 10 for carrying a product to a bottling and a canning device. A volume transfer type controllable pump 12 is used for the pipeline 10 for carrying the product in low-pressurized state or a non-pressurized state and the pump 12 is controlled by a sequence 16 for generating a number of constant- order control signals under the direction of a microprocessor 18. To measure the viscosity of a product in the pipeline 10 under changing temperature conditions, a viscometer is provided in a low-temperature cracking simulator 20. The low-temperature cracking simulator 20 is designed to receive a certain amount of substance to be measured from the pump 12 or an electromagnetic valve. A measurement result is supplied to a user, for example, by a printer 24.