Type identification and parameter selection for drive control in a coriolis flowmeter

• US 6,318,186 B1
• Filed: 06/28/1999
• Issued: 11/20/2001
• Est. Priority Date: 06/28/1999
• Status: Expired due to Term

• Current Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Original Assignee: Micro Motion Incorporated (Emerson Electric Company)
• Inventors: Smith, Brian T., Smith, Richard L.
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US09/344,841
• Time in Patent Office: 876 Days
• Field of Search: 738/613.54, 738/613.55, 738/613.56, 738/613.57, 738/61
• US Class Current: 73/861.356
• CPC Class Codes: G01F 1/8413 means for influencing the flowmeter's motional or vibrational behaviour, e.g., conduit support or fixing means, or conduit attachments
• CPC Class Codes: G01F 1/8418 motion or vibration balancing means
• CPC Class Codes: G01F 1/8436 signal processing
• CPC Class Codes: G01F 1/8477 with multiple measuring conduits
• CPC Class Codes: G01F 1/849 having straight measuring conduits

Abstract

A system for initializing parameters of a transmitter connected to a Coriolis flowmeter. This invention applies initial drive signals to a drive circuit which causes a flow tube to vibrate. The type of the flow tube is then determined from signals received from pick-off sensors associated with the flow tube. Parameters for generation of said drive signals are then set based upon the type of said flow tube.

Claims

1. A method for operating a transmitter of a Coriolis flowmeter having at least one flow tube, a driver that oscillates said at least one flow tube, and sensors affixed to said at least one flow tube that produce pickoff signals representing motion of said at least one flow tube, said method comprising the steps of:

applying initial drive signals to said driver which causes said flow tube to vibrate;

determining a frequency of oscillation of said flow tube based on said pickoff signals;

determining a type of said flow tube in response to said pickoff signals indicating said frequency of oscillation of said flow tube; and

setting parameters for generation of said drive signal in response to a determination of said type of said flow tube.

2. The method of claim 1 wherein said step of determining said type of said flow tube comprises the steps of:

comparing said frequency of oscillation to a threshold frequency; and

determining said type of said flow tube is a straight flow tube responsive to said frequency of oscillation being greater than said threshold frequency.

3. The method of claim 2 wherein said step of determining said type of said flow tube further comprises the step of:

determining said type of said flow tube is a curved flow tube responsive to said frequency of oscillation being less than or equal to said threshold frequency.

4. A product used with a transmitter connected to a Coriolis flowmeter having at least one flow tube, a driver that oscillates said at least one flow tube, and sensors affixed to said at least one flow tube that produce pickoff signals representing motion of said at least one flow tube, said product comprising:

a processor readable media for storing instructions; and

instructions for directing a processor in said product to;

generate initial drive signals for said driver to cause said flow tube to vibrate,

apply said drive signals to said driver which causes said flow tube to vibrate,

determine a frequency of oscillation of said flow tube based on said pickoff signals,

determine a type of said flow tube in response to said pickoff signals indicating said frequency of oscillation of said flow tube, and

set parameters for generation of said drive signal in response to a determination of said type of said flow tube.

5. The product of claim 4 wherein said instructions to determine said type of said flow tube comprises:

instructions for directing said processor to;

compare said frequency of oscillation to a threshold frequency; and

determine said type of said flow tube is a straight flow tube responsive to said frequency of oscillation being greater than said threshold frequency.

6. The product of claim 5 wherein said instructions to determine said type of said flow tube comprises:

instructions for directing said processor to;

determine said type of said flow tube is a curved flow tube responsive to said frequency of oscillation being less than or equal to said threshold frequency.

7. An apparatus used with a transmitter connected to a Coriolis flowmeter having at least one flow tube, a driver that oscillates said at least one flow tube, and sensors affixed to said at least one flow tube that produce pickoff signals representing motion of said at least one flow tube, said apparatus comprising:

means for applying initial drive signals to said driver which causes said flow tube to vibrate;

means for determining a frequency of oscillation of said flow tube based on said pickoff signals;

means for determining a type of said flow tube in response to said pickoff signals indicating said frequency of oscillation of said flow tube; and

means for setting parameters for generation of said drive signal in response to a determination of said type of said flow tube.

8. The apparatus of claim 10 wherein said means of determining said type of said flow tube comprises:

means for comparing said frequency of oscillation to a threshold frequency; and

means for determining said type of said flow tube is a straight flow tube responsive to said frequency of oscillation being greater than said threshold frequency.

9. The apparatus of claim 8 wherein said means of determining said type of said flow tube further comprises:

means for determining said type of said flow tube is a curved flow tube responsive to said frequency of oscillation being less than or equal to said threshold frequency.