Patent ID: 7213440

Claim:
A reference source cell for producing a predetermined flow of a fluid in a fluid outlet, comprising: a substantially sealed volume having a fluid outlet, wherein the sealed volume comprises a heat exchanger; a temperature sensing apparatus in the substantially sealed volume; temperature affecting apparatus for changing the temperature of a fluid in the sealed volume, wherein the temperature affecting apparatus comprises at least one thermo-electric device; a control arrangement for receiving an input signal indicating a predetermined fluid flow of the fluid and for controlling the temperature affecting apparatus to achieve the predetermined fluid flow in the fluid outlet by selectively heating and cooling the fluid in the sealed volume, wherein the control arrangement couples a temperature controlling electrical signal to the thermo-electric device, and responds to temperature representing electrical signals from the temperature sensing apparatus to modify the temperature controlling electrical signal; and a pressure sensing apparatus in fluid communication with the sealed volume, wherein the pressure sensing apparatus generates pressure representing electrical signals and the control arrangement responds to the pressure representing electrical signals to the control the temperature controlling signals.