Method for operating a flowmeter and respective flowmeter

Abstract

Described and shown is a method for operating a flowmeter (1) having a measuring tube (2), wherein the flow (d) of a medium (4) through the measuring tube (2) is measured. A continuous dwell time of the measured flow (d) greater than or equal to a flow threshold (d.sub.s) is assigned to a flow interval (t.sub.D,1, t.sub.D,2) and a flow volume (V.sub.1, V.sub.2) is determined from the measured flow (d) in the flow interval (t.sub.D,1, t.sub.D,2). In each case, a continuous dwell time of the measured flow (d) less than the flow threshold (d.sub.s) is assigned to a zero flow interval (t.sub.N,1). In each case, a deviation volume of the flow volume (V.sub.1, V.sub.2) in one of the flow intervals (t.sub.D,1, t.sub.D,2) from a reference flow volume is determined and the deviation volume is compared to a threshold deviation volume. If the deviation volume in one of the flow intervals (t.sub.D,1, t.sub.D,2) is less than the threshold deviation volume, a zero flow through the measuring tube (2) is determined and compensated using the measured flow (d) in the zero flow interval (t.sub.N,1) directly preceding the flow interval (t.sub.D,1, t.sub.D,2).

Claims

1. A method for operating a flowmeter having a measuring tube, wherein the flow (d) of a medium through the measuring tube is measured, wherein in a first flow interval (t.sub.D,1), a first continuous dwell time of the measured flow (d) greater than or equal to a flow threshold (d.sub.s) is assigned to the first flow interval (t.sub.D,1) and a first flow volume (V.sub.1) is determined from the measured flow (d) in the first flow interval (t.sub.D,1), in a zero flow interval (t.sub.N,1), a continuous dwell time of the measured flow (d) less than the flow threshold (d.sub.s) is assigned to the zero flow interval (t.sub.N,1), in a second flow interval (t.sub.D,2), a second continuous dwell time of the measured flow (d) greater than or equal to a flow threshold (d.sub.s) is assigned to the second flow interval (t.sub.D,2) and a second flow volume (V.sub.2) is determined from the measured flow (d) in the second flow interval (t.sub.D,2), a first deviation volume of the first flow volume (V.sub.1) in the first flow interval (t.sub.D,1) and a second deviation volume of the second flow volume (V.sub.2) in the second flow interval (t.sub.D,2), from a reference flow volume are determined and the first deviation volume and the second deviation volume are compared to a threshold deviation volume, when the first deviation volume is less than the threshold deviation volume, a zero flow through the measuring tube is determined and compensated using the measured flow (d) in the zero flow interval (t.sub.N,1) directly preceding the first flow interval (t.sub.D,1), and when the second deviation volume is less than the threshold deviation volume, a zero flow through the measuring tube is determined and compensated using the measured flow (d) in the zero flow interval (t.sub.N,1) directly preceding the second flow interval (t.sub.D,2).

2. The method according to claim 1, wherein the reference flow volume is determined from at least one of the first flow volumes (V.sub.1) or the second flow volume (V.sub.2).

3. The method according to claim 2, wherein the reference flow volume is determined in that one of the first flow volumes (V.sub.1) or the second flow volume (V.sub.2) is assigned to the reference flow volume.

4. The method according to claim 2, wherein the reference flow volume is determined in that an average value of at least two of the flow volumes is determined and assigned to the reference flow volume.

5. The method according to claim 1, wherein the first flow volume (V.sub.1) is determined in a first sub-interval of the first flow interval (t.sub.D,1), and the second flow volume (V.sub.2) is determined in a second sub-interval of the second flow interval (t.sub.D,2).

6. The method according to claim 1, wherein the measured flow (d), in each case, is used in a sub-interval (t.sub.N,1) of a zero flow interval (t.sub.N,1).

7. The method according to claim 1, wherein, when the first deviation volume is less than the threshold deviation volume, a continuous dwell time of the measured volume (d) less than the flow threshold (d.sub.s) is assigned to the zero flow interval (t.sub.N,1), wherein the zero flow interval (t.sub.N,1) directly precedes the first flow interval (t.sub.D,1), and when the second deviation volume is less than the threshold deviation volume, a continuous dwell time of the measured volume (d) less than the flow threshold (d.sub.s) is assigned to the zero flow interval (t.sub.N,1), wherein the zero flow interval (t.sub.N,1) directly precedes the second flow interval (t.sub.D,2).

8. The method according to claim 1, wherein the zero flow is determined using the measured flow (d) of at least two zero flow intervals (t.sub.N,1), in that a moving average is formed from the measured flow (d) in the at least two zero flow intervals (t.sub.N,1) or in that a median filter is used on the measured flow (d) in the at least two zero flow intervals (t.sub.N,1).

9. A flowmeter having a measuring tube and a controller, wherein the controller measures the flow (d) of a medium through the measuring tube during operation, wherein, during operation, the controller stores a flow threshold (d.sub.s), a reference flow volume and a threshold deviation volume, assigns, in a first flow interval (t.sub.D,1), a first continuous dwell time of the measured flow (d) greater or equal to the flow threshold (d.sub.s) to the first flow interval (t.sub.D,1) and determines a first flow volume (V.sub.2) from the measured flow (d) in the first flow interval (t.sub.D,2), assigns a continuous dwell time of the measured flow (d) less than the flow threshold (d.sub.s) to the zero flow interval (t.sub.N,1), assigns, in a second flow interval (t.sub.D,2), a second continuous dwell time of the measured flow (d) greater or equal to the flow threshold (d.sub.s) to the second flow interval (t.sub.D,2) and determines a second flow volume (V.sub.2) from the measured flow (d) in the second flow interval (t.sub.D,2), determines a first deviation volume of the first flow volume (V.sub.1) in the first flow intervals (t.sub.D,1) and a second deviation volume of the second flow volume (V.sub.2) in the second flow interval (t.sub.D,2), from the reference flow volume and compares the first deviation volume and the second deviation volume to the threshold deviation volume, when the first deviation volume is less than the threshold deviation volume, determines and compensates the zero flow through the measuring tube using the measured flow (d) in the zero flow interval (t.sub.N,1) directly preceding the first flow interval (t.sub.D,1), and when the second deviation volume is less than the threshold deviation volume, determines and compensates the zero flow through the measuring tube using the measured flow (d) in the zero flow interval (t.sub.N,1) directly preceding the second flow interval (t.sub.D,2).

10. A method of operating a flowmeter, the flowmeter comprising a measuring tube and a controller, the method comprising: using the measuring tube and the controller, measuring a first measured flow and a first continuous dwell time of the first measured flow during a first flow interval when the first measured flow is greater than or equal to a flow threshold; by the controller, determining a first flow volume based on the first measured flow and the first continuous dwell time; using the measuring tube and the controller, measuring a measured zero flow and a zero flow continuous dwell time of the measured zero flow during a zero flow interval when the measured zero flow is less than the flow threshold; using the measuring tube and the controller, measuring a second measured flow and a second continuous dwell time of the second measured flow during a second flow interval when the second measured flow is greater than or equal to the flow threshold; by the controller, determining a second flow volume based on the second measured flow and the second continuous dwell time; by the controller, determining a deviation volume of the second flow volume based on a reference flow volume, and comparing the deviation volume to a threshold deviation volume; when the deviation volume is less than the threshold deviation volume, compensating, by the controller, the second measured flow based on the measured zero flow, wherein the zero flow interval directly precedes the second flow interval.

11. The method according to claim 10, wherein the reference flow volume is the first flow volume.

12. The method according to claim 10, wherein the reference flow volume is an average of a plurality of preceding flow volumes determined by the controller.

13. The method according to claim 10, wherein determining the deviation volume comprises subtracting the second flow volume from the reference flow volume.

14. The method according to claim 10, wherein compensating the second measured flow based on the measured zero flow comprises subtracting the measured zero flow from the second measured flow.

15. The method according to claim 10, wherein compensating the second measured flow based on the measured zero flow comprises: by the controller, determining within the zero flow interval a zero flow sub-interval excluding asymptotic transient responses of the measured zero flow; by the controller, determining the measured zero flow within the zero flow sub-interval; and by the controller, compensating the second measured flow based on the measured zero flow within the zero flow sub-interval.

16. A flowmeter comprising: a measuring tube; and a controller, wherein the controller is configured: to use the measuring tube to measure a first measured flow and a first continuous dwell time of the first measured flow during a first flow interval when the first measured flow is greater than or equal to a flow threshold; to determine a first flow volume based on the first measured flow and the first continuous dwell time; to use the measuring tube to measure a measured zero flow and a zero flow continuous dwell time of the measured zero flow during a zero flow interval when the measured zero flow is less than the flow threshold; to use the measuring tube to measure a second measured flow and a second continuous dwell time of the second measured flow during a second flow interval when the second measured flow is greater than or equal to the flow threshold; to determine a second flow volume based on the second measured flow and the second continuous dwell time; to determine a deviation volume of the second flow volume based on a reference flow volume, and comparing the deviation volume to a threshold deviation volume; when the deviation volume is less than the threshold deviation volume, to compensate, the second measured flow based on the measured zero flow, wherein the zero flow interval directly precedes the second flow interval.

17. The flowmeter according to claim 16, wherein the reference flow volume is the first flow volume.

18. The flowmeter according to claim 16, wherein the controller determines the deviation volume by subtracting the second flow volume from the reference flow volume.

19. The flowmeter according to claim 16, wherein the controller compensates the second measured flow based on the measured zero flow by subtracting the measured zero flow from the second measured flow.

20. The flowmeter according to claim 16, wherein the controller compensates the second measured flow based on the measured zero flow by: determining within the zero flow interval a zero flow sub-interval excluding asymptotic transient responses of the measured zero flow; determining the measured zero flow within the zero flow sub-interval; and compensating the second measured flow based on the measured zero flow within the zero flow sub-interval.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings show:

(2) FIG. 1 is an embodiment of the flowmeter according to the invention,

(3) FIG. 2 is a flow measured by the flowmeter, and

(4) FIG. 3 is the flow chart of an embodiment of the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) The embodiment schematically shown in FIG. 1 of the flowmeter 1 according to the invention is a magnetic-inductive flowmeter. It has a measuring tube 2 and a controller 3 and is integrated in a filling process of a medium 4. The filling process consists essentially of a first and a second filling step, which are continually repeated. In the first filling step, the medium 4 is conveyed, whereby is also flows through the measuring tube 2. In the second filling step, the medium 4 is no longer conveyed, whereby it is stagnant 2 in the measuring tube. Since the flowmeter 1 is in operation, the controller 3 measures the flow d over the time t shown in FIG. 2 and carries out the method according to the invention as shown in the flow chart in FIG. 3.

(6) The method according to the invention comprises the following method steps:

(7) In a first method step 5, a first and a second continuous dwell time of the measured flow d greater than or equal to a flow threshold d.sub.s are assigned to a first flow interval t.sub.D,1 and a second flow interval t.sub.D,2. The first flow interval t.sub.D,1 and the second flow interval t.sub.D,2 each correspond to a first filling step. Further, using integration, a first flow volume V.sub.1, is determined from the measured flow d in the entire first flow interval t.sub.D,1, and a second volume V.sub.2 is determined from the measured flow d in the entire second flow interval t.sub.D,2.

(8) Then, in a second method step 6, the deviation volume of the flow volume V.sub.2 in the second flow interval t.sub.D,2 is determined by subtraction from a reference flow volume and the deviation volume is compared to a threshold deviation volume. Thereby, the reference flow volume is determined from the first flow volume V.sub.1, in that the first flow volume V.sub.1 is assigned to the reference flow volume.

(9) Then, in a third method step 7, a continuous dwell time of the measured flow d less than the flow threshold d.sub.s is assigned to a zero flow interval t.sub.N,1, since the deviation volume in the second flow interval t.sub.D,2 is less than the threshold deviation volume. The zero flow interval t.sub.N,1 corresponds to a second filling step. Although the medium 4 in the measuring tube 2 is stagnant, the flow d measured by the flowmeter 1 is greater than zero. Consequently, the zero flow is greater than zero, whereby the measured flow d of the flowing medium 4 is afflicted by a constant measurement error in the amount of the zero flow.

(10) Then, in a fourth method step 8, the zero flow through the measuring tube 2 is determined and compensated using the measured flow d in the first zero flow interval t.sub.N,1 directly preceding the second flow interval t.sub.D,2 since the deviation volume in the second flow interval t.sub.D,2 is less than the threshold deviation volume. The compensation of the zero flow is carried out by subtraction of the zero flow from the measured flow d, whereby the constant measurement error caused by the zero flow is at least reduced. The measured flow d in a sub-interval t.sub.N,1 of the first zero flow interval t.sub.N,1 is used thereby. The duration of the sub-interval t.sub.N,1 in the zero flow interval t.sub.N,1 is dimensioned so that the asymptotic transient responses of the flow d within the sub-interval have already sufficiently subsided.

REFERENCE NUMBERS

(11) 1 Flowmeter 2 Measuring tube 3 Controller 4 Medium 5 First method step 6 Second method step 7 Third method step 8 Fourth method step d Flow d.sub.s Flow threshold t Time t.sub.D,1 First flow interval t.sub.D,2 Second flow interval t.sub.N,1 Zero flow interval t.sub.N,1 Sub-interval V.sub.1 First flow volume V.sub.2 Second flow volume