Coriolis flow meter.
The Corilolis flow meter is basically a mass flow meter. It gives you exactly the mass of CO2 is delivered by the membrane pump, with at least three advantages if compared to traditional meters:
It has no moving parts. It works at full pressure at the outlet of the pump without compromising the suction flow or producing cavitation. It works with all the fluids status, gas, supercritical, liquid.
Because of its high pressure, no traditional meters are available for supercritical CO2. Of course this high performance technology is not cheap. Many system are not equipped with any flow meter to be more competitive in the price, but in this way, you will never be sure about how much and if the CO2 is really flowing in the circuit. Maybe is the expected flow or maybe nothing! Who can say it. Impossible to be sure. The Coriolis flow meter is essential to have the correct feedback and control the CO2 flow in the circuit. The full automation system detects the feedback from the flow meter and drive the motor to give exactly the expected kg/hr. This is irrelevant. As you can see in the pomp flow topic, lower and higher flow give less extract than optimal.