Flow cytometery system with fluidics control system
A system, method, and apparatus are provided for flow cytometry. In one example, the flow cytometry system includes dual laser devices and dual scatter channels to measure velocity of particles in a core stream of sample fluid. The total flow rate of the sample fluid and the sheath fluid around the sample fluid is controlled, and thus held constant, by a feedback control system controlling a vacuum pump based on differential pressure across ends of a flow channel in the flow cell.
1 . A control system for a flow cytometer, the control system comprising:
a controllable gas valve coupled between a vacuum chamber and a flow restrictor to an open atmosphere, wherein the controllable gas valve is responsive to a valve open signal;
a differential pressure transducer coupled across ends of a flow channel of a flow cell, the differential pressure transducer to sense over a range of pressure levels across the flow channel and generate a differential pressure signal voltage proportional to the sensed differential pressure level;
a conditioning circuit-coupled to the differential pressure transducer to reduce noise and amplify the differential pressure signal voltage;
an analog to digital converter coupled to the conditioning circuit to receive the amplified differential pressured signal voltage, the analog to digital converter to periodically convert a continuous time analog signal form of the amplified differential pressure signal voltage into a time sampled digital form of the amplified differential pressure signal voltage generating a digital differential pressure signal;
a control logic device coupled to the analog to digital converter, the control logic device including
a pressure calculator to periodically determine a pressure level based on the digital differential pressure signal,
a delay loop counter coupled to the pressure calculator to periodically generate a leak bit to allow the generation of the valve open signal for the controllable gas valve while a vacuum pump coupled to the vacuum chamber is operational, and
a control logic to periodically generate the valve open signal for the controllable gas valve in response to the generation of the leak bit to increase pressure in the vacuum chamber and reduce differential pressure across the ends of the flow channel.
2 . The control system of claim 1 , wherein
the control logic further generates the valve open signal when setting up the flow cytometer prior to testing a fluid sample.
3 . The control system of claim 1 , wherein
the control logic disallows the periodic generation of the valve open signal when the vacuum pump coupled to the vacuum chamber is non-operational.
4 . The control system of claim 1 , further comprising:
a driver circuit coupled between the control logic device and the controllable gas valve, the driver circuit to amplify voltage of the valve open signal to control the controllable gas valve into an open position to vent the vacuum chamber to the open atmosphere through the flow restrictor.
5 . The control system of claim 1 , wherein
the conditioning circuit includes a gain amplifier.
6 . The control system of claim 2 , wherein
the setting up of the flow cytometer includes one or more of degassing, sample load change, and flushing.