Patent ID: 8795982

Claim:
An indirect pressure sensing system for non-invasive measurement of activity levels in a biological component of a liquid phase in a sealed container, wherein the system communicates primary pressure variations of less than 1 bar from within the container, via a thin flexible, non-toxic gas-impermeable diaphragm, to a closed secondary chamber that contains compressible gas and an electronic pressure sensor or a connection to an electronic pressure sensor, wherein there is a defined relationship between the primary and secondary pressures, which enables the pressure sensor in the secondary chamber to generate a signal representing primary pressure in the sealed container, but to remain isolated from the contents of the sealed container, wherein said sealed container is partially filled with liquid, wherein pressure variations arise in the gaseous phase of the headspace of the container due to biological activity within the liquid, and wherein said container includes a sealable inlet port and a mixer to promote gas exchange between a liquid phase and a gaseous phase, wherein said mixer is driven indirectly by one or more external magnets coupled to said mixer through walls of said sealed container.