Method and apparatus for pulse gas delivery using an external pressure trigger
A fluid control system and associated method for pulse delivery of a fluid includes a shutoff valve and a mass flow controller (MFC) upstream of the shutoff valve. The MFC includes a flow channel, a control valve to control flow of fluid in the flow channel, a flow sensor to measure flow rate in the flow channel, and a controller having a valve input from the shutoff valve indicating opening of the shutoff valve. The controller is configured to respond to the valve input to control flow of fluid through the control valve to initiate and terminate a pulse of fluid from the flow channel to the shutoff valve to control a mass of fluid delivered during the pulse of fluid. The valve input can be a pressure signal, and the MFC can include a pressure sensor to sense the pressure signal.
1. A mass flow controller (MFC) for pulse delivery of a fluid, the MFC comprising:
a flow channel;
a control valve to control flow of fluid in the flow channel;
a flow sensor to measure flow rate in the flow channel; and
a controller having an external input and being configured to calculate a mole set point n sp from a flow set point Q sp and a pulse-on period Δt, the controller configured to respond to the external input to control flow of fluid through the control valve to initiate a pulse of fluid from the flow channel to control a mass of fluid delivered during the pulse of fluid, the pulse of fluid being terminated in response to the calculated mole set point n sp .
2. The MFC of claim 1 , wherein the controller controls the flow of fluid through the control valve based on feedback from the flow sensor during the pulse of fluid.
3. The MFC of claim 1 , wherein the external input is a pressure signal, and wherein the MFC includes a pressure sensor to sense the pressure signal.
4. The MFC of claim 3 , wherein the pressure sensor is configured to receive the pressure signal via a tap into a pneumatic line, pressure in the pneumatic line opening and closing a shutoff valve.
5. The MFC of claim 3 , wherein the pressure sensor is configured to receive the pressure signal via a pneumatic line controlled by a host controller.
6. The MFC of claim 3 , wherein the controller is configured to convert a rising edge of the pressure signal into a trigger signal for starting pulse gas delivery.
7. The MFC of claim 1 , wherein the mole set point n sp is a targeted amount of the mass of fluid to be delivered during the pulse of fluid.
8. The MFC of claim 7 , wherein the pulse-on period Δt is a default value stored in the MFC and the flow set point Q sp is received from a host controller.
9. The MFC of claim 8 , wherein the MFC is programmable to change the pulse-on period Δt from the stored default value.
10. The MFC of claim 1 , wherein the controller is configured to close the control valve based on a computation of the mass of fluid delivered and/or the duration of the pulse-on period Δt during the pulse of fluid.
11. A method of delivering a pulse of fluid, the method comprising:
receiving a flow set point Q SP ;
calculating a mole set point n sp from the flow set point Q sp and a pulse-on period Δt;
controlling flow of fluid into a flow channel with a control valve;
measuring flow rate in the flow channel with a flow sensor; and
responding to an external input to control flow of fluid through the control valve to initiate a pulse of fluid from the flow channel to control a mass of fluid delivered during the pulse of fluid, the pulse of fluid being terminated in response to the calculated mole set point n sp .
12. The method of claim 11 , wherein controlling the flow of fluid through the control valve is based on feedback from the flow sensor during the pulse of fluid.
13. The method of claim 11 , wherein responding to the external input includes sensing a pressure signal.
14. The method of claim 13 , wherein the pressure signal is received via a tap into a pneumatic line, pressure in the pneumatic line opening and closing a shutoff valve.
15. The method of claim 14 , further comprising controlling opening and closing of the shutoff valve.
16. The method of claim 13 , further comprising converting a rising edge of the pressure signal into a trigger signal for starting pulse gas delivery.
17. The method of claim 11 , wherein the mole set point n sp is a targeted amount of the mass of fluid to be delivered during the pulse of fluid.
18. The method of claim 11 , wherein the pulse-on period Δt is a default value stored in a mass flow controller (MFC) and the flow set point Q sp is received from a host controller.
19. The method of claim 18 , further comprising changing the pulse-on period Δt from the stored default value.
20. The method of claim 11 , further comprising closing the control valve based on a computation of the mass of fluid delivered and/or the duration of the pulse-on period Δt during the pulse of fluid.