FLUID FLOW MEASURING SYSTEM

• US 3,650,151 A
• Filed: 11/18/1970
• Issued: 03/21/1972
• Est. Priority Date: 11/18/1970
• Status: Expired due to Term

• Current Assignee: Millipore Corporation (Merck & Co., Inc.)
• Original Assignee: Charles F. Drexel
• Inventors: Drexel, Charles F.
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US05/090,556
• Time in Patent Office: 489 Days
• Field of Search: 73/194R,194E,194M,195,196,29 137/101.19
• US Class Current: 73/861.04
• CPC Class Codes: G01F 1/6847 where sensing or heating elements are not disturbing the fluid flow, e.g. elements mounted outside the flow duct
• CPC Class Codes: G01F 1/74 Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
• CPC Class Codes: G05D 11/132 by controlling the flow of the individual components G05D11/133 takes precedence
• CPC Class Codes: Y10S 261/65 Vaporizers
• CPC Class Codes: Y10T 137/2529 With electrical controller

Abstract

A control system for the vaporization of a liquid by a carrier gas in which the carrier gas passes through a first set of resistance elements in a terminal conductivity cell, then through a mass flow sensor and, via a throttling valve, into a vaporizing tank of diluent where the carrier gas picks up diluent vapor and then passes through a second set of resistance elements in the thermal conductivity cell. The resistance elements are connected in a bridge circuit yielding an output voltage representing the volume ratio of diluent to carrier gas. This voltage is multiplied by the voltage derived from the mass flow sensor to yield a voltage which represents the absolute value of mass flow rate of diluent. This value is compared to a desired value, the differential being amplified and utilized to control the throttling valve.

Claims

1. A measuring system for determining the amount of first fluid carried by a carrier gas, comprising:

means for mixing said carrier gas with said first fluid, means for monitoring the ratio of said mixed first fluid to said carrier gas and generating a first signal in correspondence to said ratio;

means for monitoring the mass flow of said carrier gas and generating a second signal in correspondence thereto; and

means for multiplying said first and second signals to yield a third signal in representation of the mass flow of said first fluid.

2. The invention according to claim 1 including means for modulating the flow of said carrier gas in correspondence to said third signal.

3. The invention according to claim 1 in which said ratio monitoring means comprises a thermal conductivity cell and means for passing said first fluid mixed with said carrier gas through said cell to generate said first signal.

4. The invention according to claim 3 in which said thermal conductivity cell comprises a diffusion-type cell.

5. The invention according to claim 1 in which said ratio monitoring means comprises a thermal conductivity cell including at least one resistance element upstream of said mixing means, means for passing said carrier gas in contact with said upstream resistance element prior to passage through said mixing means, at least one resistance element downstream of said mixing means, and means for passing said first fluid mixed with said carrier gas in contact with said downstream resistance element, whereby to generate said first signal.

6. The invention according to claim 1 in which said mass flow monitor comprises a conduit for said carrier gas upstream of said mixing means, a heater element for heating said carrier gas as it passes through said conduit, and thermally responsive resistance elements on opposite sides of said heater element, whereby to generate said second signal.

7. The invention according to claim 1 in which (1) said ratio monitoring means comprises a diffusion-type thermal conductivity cell including at least one resistance element upstream of said mixing means, means for passing said carrier gas through said upstream resistance element prior to passage through said mixing means, at least one resistance element downstream of said mixing means, and means for passing said first fluid mixed with said carrier gas through said downstream resistance element, whereby to generate said first signal, and (2) said mass flow monitor comprises a conduit for said carrier gas upstream of said mixing means, a heater element for heating said carrier gas as it passes through said conduit, and thermally responsive resistance elements on opposite sides of said heater element, whereby to generate said second signal.

8. The invention according to claim 1 in which said first fluid comprises a liquid which can be vaporized by said carrier gas, and said mixing means comprises a reservoir of said liquid.

9. The invention according to claim 8 in which said liquid is silicon tetrachloride and said carrier gas is hydrogen.