Magnetic-Inductive Flowmeter and Method of Operating the Same

Abstract

A magnetic-inductive flowmeter and a method for operating the flowmeter are disclosed. The flowmeter has a measuring tube, a magnetic field generator, and a controller with first and second measuring terminals. A medium is made to flow through the measuring tube. The controller performs the following steps: generating and feeding an emission signal and receiving a receive signal caused by the emission signal at the first measuring terminal and second measuring terminal; determining an impedance with an impedance amount and an impedance phase using the emission signal and the receive signal; and signaling a short circuit if the impedance amount is smaller than a first limit impedance amount and the impedance phase is larger than a limit impedance phase.

Claims

1. A method for operating a magnetic-inductive flowmeter, wherein the magnetic-inductive flowmeter includes a measuring tube, a magnetic field generator, a first measuring electrode, a second measuring electrode, a first measuring line, a second measuring line and a controller having a first measuring terminal and a second measuring terminal wherein, on the one hand, the first measuring electrode and the first measuring terminal are electrically connected to one another via the first measuring line and, on the other hand, the second measuring electrode and the second measuring terminal are electrically connected to one another via the second measuring line, wherein a medium is made to flow through the measuring tube, wherein a magnetic field is generated by the magnetic field generator in the medium flowing through the measuring tube, so that a flow signal present between the first measuring terminal and the second measuring terminal is induced in the medium, wherein a flow rate of the medium through the measuring tube is determined by the controller using the flow signal, the method comprising: generating and feeding a transmission signal and receiving a receive signal caused by the transmission signal at the first measuring terminal and second measuring terminal; determining an impedance having an impedance amount and an impedance phase using the transmission signal and the receive signal; and signaling a short circuit when the impedance amount is less than a first limit impedance amount and the impedance phase is greater than a limit impedance phase.

2. The method according to claim 1, wherein the magnetic-inductive flowmeter includes a third measuring line and a fourth measuring line and the controller includes a third measuring terminal and a fourth measuring terminal; wherein, on the one hand, the first measuring electrode and the third measuring terminal are electrically connected to one another via the third measuring line and, on the other hand, the second measuring electrode and the fourth measuring terminal are electrically connected to one another via the fourth measuring line; wherein, on the one hand, a line impedance of the first measuring line is determined by the controller using the transmission signal and a first measuring signal present between the first measuring terminal and the third measuring terminal and, on the other hand, a line impedance of the second measuring line is determined using the transmission signal and a second measuring signal present between the second measuring terminal and the fourth measuring terminal; and wherein the line impedance of the first measuring line and the line impedance of the second measuring line are taken into account by the controller when determining the impedance.

3. The method according to claim 1, wherein the first limit impedance is selected as 50 ohms and the impedance phase is selected as −10°.

4. The method according to claim 1, wherein a short circuit is also signaled when the impedance amount is smaller than a second limit impedance amount independent of the impedance phase; and wherein the second limit impedance amount is smaller than the first limit impedance amount.

5. The method according to claim 4, wherein the second limiting impedance amount is selected as 2 ohms.

6. The method according to claim 1, wherein the transmission signal is generated by the controller with a frequency between 500 Hz and 1 kHz.

7. The method according to claim 1, wherein the transmission signal is generated by the controller with two frequencies between 500 Hz and 1 kHz.

8. The method according to claim 1, wherein the step of determining the impedance is performed by the controller with additional use of a length of the first measuring line and a length of the second measuring line.

9. A magnetic-inductive flowmeter, comprising: a measuring tube; a magnetic field generator; a first measuring electrode; a second measuring electrode; a first measuring line; a second measuring line; and a controller with a first measuring terminal and a second measuring terminal; and wherein, on the one hand, the first measuring electrode and the first measuring terminal are electrically connected to one another via the first measuring line and, on the other hand, the second measuring electrode and the second measuring terminal are electrically connected to one another via the second measuring line; wherein the magnetic field generator is designed to generate a magnetic field in a medium flowing through the measuring tube, so that a flow signal present between the first measuring terminal and the second measuring terminal is induced in the medium; wherein the controller is designed to determine a flow rate of the medium through the measuring tube using the flow signal; wherein the controller is designed as follows: generating and feeding a transmission signal and receiving a receive signal caused by the transmission signal at the first measuring terminal and second measuring terminal; determining an impedance having an impedance amount and an impedance phase using the transmission signal and the receive signal; and signaling a short circuit when the impedance amount is less than a first limit impedance amount and the impedance phase is greater than a limit impedance phase.

10. The magnetic-inductive flowmeter according to claim 9, wherein the magnetic-inductive flowmeter has a third measuring line and a fourth measuring line and the controller has a third measuring terminal and a fourth measuring terminal; wherein, on the one hand, the first measuring electrode and the third measuring terminal are electrically connected to one another via the third measuring line and, on the other hand, the second measuring electrode and the fourth measuring terminal are electrically connected to one another via the fourth measuring line; wherein the controller is designed, on the one hand, to determine a line impedance of the first measuring line using the transmission signal and a first measuring signal present between the first measuring terminal and the third measuring terminal and, on the other hand, to determine a line impedance of the second measuring line using the transmission signal and a second measuring signal present between the second measuring terminal and the fourth measuring terminal; and wherein the controller is designed to take into account the line impedance of the first measuring line and the line impedance of the second measuring line when determining the impedance.

11. (canceled)

12. A method for operating a magnetic-inductive flowmeter, comprising: generating and feeding a transmission signal to a first measuring terminal and a second measuring terminal; receiving a receive signal caused by the transmission signal at the first measuring terminal and second measuring terminal; determining an impedance having an impedance amount; determining an impedance phase using the transmission signal and the receive signal; and signaling a short circuit when the impedance amount is less than a first limit impedance amount and the impedance phase is greater than a limit impedance phase.

13. The method according to claim 12, further comprising: determining a first line impedance of a first measuring line using the transmission signal and a first measuring signal present between the first measuring terminal and a third measuring terminal, wherein the first measuring line electrically connects the first measuring terminal to a first electrode; determining a second line impedance of a second measuring line using the transmission signal and a second measuring signal present between the second measuring terminal and a fourth measuring terminal, wherein the second measuring line electrically connects the second measuring terminal to a second electrode; wherein the step of determining the impedance involves taking into account the first line impedance and the second line impedance.

14. The method according to claim 12, wherein the first limit impedance is 50 ohms and the impedance phase is −10°.

15. The method according to claim 12, further comprising: signaling a second short circuit when the impedance amount is smaller than a second limit impedance amount independent of the impedance phase; and wherein the second limit impedance amount is smaller than the first limit impedance amount.

16. The method according to claim 12, wherein the second limit impedance is 2 ohms.

17. The method according to claim 12, wherein the transmission signal has a frequency between 500 Hz and 1 kHz.

18. The method according to claim 12, wherein the transmission signal has two frequencies between 500 Hz and 1 kHz.

19. The method according to claim 12, wherein the step of determining the impedance involves use of a length of the first measuring line and a length of the second measuring line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In detail, a multitude of possibilities are provided for designing and further developing the magnetic-inductive flowmeter and the method for operating a magnetic-inductive flowmeter. For this purpose, reference is made to the following description of preferred embodiments in connection with the drawings.

[0029] FIG. 1 illustrates an embodiment of a magnetic-inductive flowmeter in a first view.

[0030] FIG. 2 illustrates the embodiment in a second view.

[0031] FIG. 3 illustrates a flowchart of an embodiment of a method for operating the magnetic-inductive flowmeter.

DETAILED DESCRIPTION

[0032] FIGS. 1 and 2 show in different views an abstracted representation of essential components of an embodiment of a magnetic-inductive flowmeter 1. The magnetic-inductive flowmeter 1 has a measuring tube 2, a magnetic field generator 3, a first measuring electrode 4, a second measuring electrode 5, a first measuring line 6, a second measuring line 7, a third measuring line 8, a fourth measuring line 9 and a controller 10 with a first measuring terminal 11, a second measuring terminal 12, a third measuring terminal 13 and a fourth measuring terminal 14.

[0033] The first measuring electrode 4 is electrically connected to the first measuring terminal 11 via the first measuring line 6 and to the third measuring terminal 13 of the controller 10 via the third measuring line 8. The second measuring electrode 5 is electrically connected on the one hand to the second measuring terminal 12 via the second measuring line 7 and on the other hand to the fourth measuring terminal 14 via the fourth measuring line 9.

[0034] The magnetic field generator 3 is designed to generate a magnetic field 15 in a medium 16 flowing through the measuring tube 2, so that a flow signal present between the first measuring terminal 11 and the second measuring terminal 12 is induced in the medium 16.

[0035] The controller 10 is designed to determine a flow rate of the medium 16 through the measuring tube 2 using the flow rate signal.

[0036] FIGS. 1 and 2 show the magnetic-inductive flowmeter 1 during operation, and therefore the medium 16 is made to flow through the measuring tube 2 and the magnetic field generator 3 generates the magnetic field 15 in the medium 16 flowing through the measuring tube 2 so that the flow signal present between the first measuring terminal 11 and the second measuring terminal 12 is induced into the medium 16. The magnetic field generator 3 is thereby controlled by the controller 10.

[0037] The controller 10 determines the flow rate of the medium 16 through the measuring tube 2 using the flow rate signal.

[0038] FIG. 3 shows a flowchart of an embodiment of a method for operating the magnetic-inductive flowmeter 1. The controller 10 is designed to perform this method and performs it since the magnetic-inductive flowmeter 1 is in operation.

[0039] In a first method step 101, an emission signal is generated and fed to the first measuring terminal 11 and second measuring terminal 12. Further, a receive signal caused by the emission signal is received.

[0040] In the present case, the emission signal is a current signal I which is impressed into the first measuring terminal 11. The current signal flows via the first measuring line 6, the first electrode 4, the medium 16, the second measuring electrode 5, the second measuring line 7 into the second measuring terminal 12. The receive signal is a voltage signal U, which is present between the first measuring terminal 11 and the second measuring terminal 12.

[0041] In a second method step 102, an impedance having an impedance amount and an impedance phase is determined using the emission signal and the receive signal. In the present case, the impedance is determined according to Z=U/I.

[0042] Further, using the emission signal and a first measuring signal present between the first measuring terminal 11 and the third measuring terminal 13, a line impedance of the first measuring line 6 is determined, and secondly, using the emission signal and a second measuring signal present between the second measuring terminal 12 and the fourth measuring terminal 14, a line impedance of the second measuring line 7 is determined. The line impedance of the first measuring line 6 and the line impedance of the second measuring line 9 are taken into account when determining the impedance.

[0043] In the present embodiment, the current signal I flows as the emission signal through the first measuring line 6 and the second measuring line 7, but not through the third measuring line 8 and through the fourth measuring line 9. In this embodiment, the third measuring terminal 13 and the fourth measuring terminal 14 have a high input impedance, so there is no current flowing through them that affects measurements. Thus, there is also no voltage drop due to the current signal I in the third measuring line 8 and the fourth measuring line 9. The first measuring signal is a first measuring voltage U.sub.1 and the second measuring signal is a second measuring voltage U.sub.2. The line impedance of the first measuring line 6 is thus Z.sub.1=U.sub.1/I and that of the second measuring line 7 is Z.sub.2=U.sub.2/I.

[0044] In a third method step 103, a short circuit is signaled either when the impedance amount is smaller than a first limit impedance amount and the impedance phase is larger than a limit impedance phase, or, when the impedance amount is smaller than a second limit impedance amount independent of the impedance phase.

[0045] In this case, the controller 10 has been given 50 ohms as the first limit impedance amount, 2 ohms as the second limit impedance amount, and −10 degrees as the impedance phase. The emission signal is generated with two frequencies between 500 Hz and 1 kHz, namely with the frequency 500 Hz and the frequency 1 kHz.

[0046] The method and the determination of the flow do not interfere with each other because they are separated in time.