Upstream volume mass flow verification systems and methods

Patent metadata

Field	Value
Publication number	US-9952078-B2
Application number	US-201414304463-A
Country	US
Kind code	B2
Filing date	Jun 13, 2014
Priority date	Jul 24, 2009
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

This disclosure relates to mass flow verification systems for and methods of measuring and verifying the mass flow through a mass flow delivery/measurement device such as a mass flow controller. A mass flow verification system comprises a preset volume, a temperature sensor, and a pressure sensor. The measured verified flow determined by the mass flow verification system can be adjusted to compensate for errors resulting from a dead volume within the mass flow measurement device.

First claim

What is claimed:

1. An upstream mass flow verification system for improving the performance of a mass flow controller having a dead volume, the system comprising:
an upstream volume capable of storing a test fluid, wherein the upstream volume is disposed along a flow path upstream of a mass flow controller, wherein the mass flow controller is under test and includes a given dead volume;
a temperature sensor configured to sense the temperature within the upstream volume;
a pressure sensor configured to sense the fluid pressure within the upstream volume; and
a processor configured to receive temperature and pressure signals from the temperature sensor and pressure sensor, respectively, to determine the flow rate of test fluid through the mass flow controller based on the rate of decay of pressure over temperature (P/T) within the upstream volume and which compensates for flow rate errors caused by the given dead volume within the mass flow controller;
wherein the processor is configured to, in determining the flow rate of the test fluid through the mass flow controller, compensate for the given dead volume for either of (i) the case where the mass flow controller is pressure-insensitive, or (ii) the case where the mass flow controller is pressure-sensitive.

2. The system of claim 1 , wherein the processor is further configured to determine the rate of decay of pressure or temperature in accordance with the following equation,
wherein the flow is measured according to the following:

Q
=

(

V
t

-

V
d

)

·

T
stp

R
·

P
stp

·
T

·

d
⁡

(

P
/
T

)

d
⁢

⁢
t

wherein
Q is the measured flow rate,
V t the total volume of the mass flow verification (MFV) system,
V d represents the dead volume of the mass flow controller under test,
R is the universal gas constant,
P and T are the gas pressure and temperature respectively, and
P stp and T stp are the standard pressure (1.01325e5 Pa) and standard temperature (273.15K) respectively.

3. The system of claim 2 , wherein the processor is further configured to wait until the system stabilizes before making the determination of the rate of decay of pressure over temperature (P/T).

4. The system of claim 1 , wherein the dead volume is set to zero by the processor.

5. The system of claim 1 , wherein a value of the dead volume is entered by a user of the system.

6. The system of claim 1 , further comprising an input valve for controlling the flow of test fluid into the volume, and an output valve for controlling the flow of fluid from the volume through the mass flow controller, wherein the output valve is closed and input valve is opened so as to fill the volume until it reaches a measurable pressure level, and wherein the input valve is then closed, and the output valve is open to allow fluid to flow from the volume through the mass flow controller.

7. A method of improving the performance of a test mass flow measurement device that is under test and has a given dead volume, the method comprising:
with a pressure sensor, measuring an established pressure of a test fluid in a fixed volume disposed along a flow path upstream of the test mass flow measurement device;
with a temperature sensor, measuring a temperature of the test fluid in the fixed volume upstream of the test mass flow measurement device;
opening a valve to transfer the test fluid from the fixed volume through the test mass flow measurement device, wherein the valve is disposed along a flow path between the fixed volume and the test mass flow measurement device; and
determining, with a processor, a mass flow rate through the mass flow measurement device under test based on the rate of change in pressure over temperature (P/T) of the test fluid within the fixed volume,
wherein the step of determining includes compensating for flow rate errors caused by the given dead volume within the mass flow measurement device under test;
wherein, in determining the flow rate of test fluid through the mass flow measurement device, the processor is configured to compensate for the given dead volume for either of (i) the case where the mass flow measurement device is pressure-insensitive, or (ii) the case where the mass flow measurement device is pressure-sensitive.

8. The method of claim 7 , wherein determining the calculation of the mass flow rate includes determining the flow according to the following:

Q
=

(

V
t

-

V
d

)

·

T
stp

R
·

P
stp

·
T

·

d
⁡

(

P
/
T

)

d
⁢

⁢
t

wherein
Q is the measured flow rate,
V t is the total volume of the MFV system,
V d represents the given dead volume of the mass flow measurement device under test,
R is the universal gas constant,
P and T are the gas pressure and temperature respectively, and
P stp and T stp are the standard pressure (1.01325e5 Pa) and standard t

Assignees

• Mks Instr Inc

Inventors

• Ding Junhua
• Zarkar Kaveh H

Classifications

• G01F5/00 Primary

  Measuring a proportion of the volume flow · CPC title

• G01F25/00 Primary

  Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume · CPC title

• G01F1/80 Primary

  operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted · CPC title

• G01F25/0038

  Physics · mapped topic

• G01F25/0053

  Physics · mapped topic