For leak testing closed containers which are filled with a filling product containing at least one liquid component the container is introduced in a test cavity which is evacuated at least down to vapour pressure of that liquid component. In a component feeding unit, an opening provided in a suppressor for picking electronic components is formed in a size corresponding to electronic components stored in a storage tape of 16 mm pitch so as to employ storage tapes of four types, i. The front face of the probe also has mounted therein or thereon a piezoelectric transducer for detecting an acoustic response to the radiation pulses connected to a processing unit which converts the transducer signal into a measure of hemoglobin concentration andor hematocrit of blood.