Flow node to deliver process gas using a remote pressure measurement device

1. A flow node for low flow delivery of process gas, comprising:

an inlet to a conduit;

a valve seat and poppet assembly controlled by an actuator to receive a process gas;

a characterized restrictor, in series and directly adjacent with the valve seat, and to provide a primary flow restriction in accordance with one or more pressure set points while having a minimized volume between the valve seat and the characterized restrictor by being directly adjacent to each other so that bleed down time is minimized for low flow transitions, wherein a conductance of the characterized restrictor is low enough relative to the conductance of the valve seat to cause a pressure drop sufficiently large relative to the pressure drop of the valve seat assembly that the pressure drop of the valve seat poppet assembly can be ignored without introducing significant flow errors relative to the desired accuracy; and

an outlet to exhaust the process gas from the conduit at a desired mass flow.

2. The flow node of claim 1 , wherein the conduit inlet is coupled to a pressure measurement device located upstream to measure a pressure of the process gas within the conduit.

3. The flow node of claim 2 , wherein the pressure measurement device is part of an electronic regulator located upstream of the flow node.

4. The flow node of claim 1 , wherein the electronic regulator receives a pressure set point adjustment based on an external measurement of a second pressure downstream from the flow node and a temperature, to enhance accuracy in determining a pressure set point needed to generate the desired flow.

5. The flow node of claim 1 , wherein the pressure drop across the valve seat and poppet assembly is sufficiently small such that remote upstream pressure measurements sufficiently represents the pressure delivered to the restrictor in the flow node.

6. The flow node of claim 1 , wherein the pressure drop across the valve seat is less than 5% of the remote upstream pressure measurement.

7. The flow node of claim 1 , wherein the pressure drop across the valve set is less than 0.5% of the remote upstream pressure measurement.

8. The flow node of claim 1 , further comprising:

a proportional valve vent in an electronic regulator, wherein the conduit inlet is coupled to the electronic regulator with the proportional valve vent to vent the process gas from the conduit through the proportional valve vent and reduce the pressure delivered to the restrictor in the flow node faster than bleed down.

9. The flow node of claim 1 , further comprising:

an on/off valve vent in an electronic regulator, wherein the inlet conduit is coupled to the electronic regulator with the on/off valve vent with a flow limiting restrictor to vent the process gas from the conduit through the on/off valve vent and reduce the pressure delivered to the restrictor in the flow node faster than bleed down.

10. The flow node of claim 1 , wherein a ratio of conductance between the valve seat and the characterized restrictor is at least 10 to 1.

11. The flow node of claim 1 , wherein a ratio of conductance between the valve seat and the characterized restrictor is at least 200 to 1.

12. The flow node of claim 1 , further comprising:

a second characterized restrictor connecting the inlet and outlet, to bypass the valve and poppet assembly for defeating the total shut off capability of the valve and poppet assembly.

13. The flow node of claim 1 , wherein the characterized restrictor comprises one of: a laminar flow element and a sonic nozzle.