Abstract
A magnetic-inductive flowmeter for ascertaining flow velocity and/or volume flow of a medium includes a measuring tube for conveying the medium, a magnetic field producing means and at least one electrode assembly, which is installed in the measuring tube in such a manner that it forms a galvanic contact with the medium, wherein the electrode assembly has an electrode body, wherein the electrode body is stylus-shaped and has a front end surface, characterized in that a pressure measuring transducer is coupled with the electrode body, wherein the pressure measuring transducer is contactable with the pressure acting on the front end surface, and the electrode assembly includes a temperature sensor, which is adapted to ascertain a measurement signal dependent on temperature of the medium.
Claims
1-17. (canceled)
18. A magnetic-inductive flowmeter for determining a flow velocity and/or a volume flow and pressure of a medium, the flowmeter comprising: a measuring tube adapted to convey the medium; a magnetic field generating system; and at least one electrode assembly disposed in the measuring tube as to facilitate a galvanic contact with the medium, wherein the at least one electrode assembly comprises: an electrode body that is stylus-shaped and has a front end surface; a pressure measuring transducer coupled with the electrode body such that the pressure measuring transducer is contactable by a pressure acting on the front end surface; and a temperature sensor configured to determine a measurement signal dependent on a temperature of the medium.
19. The flowmeter of claim 18, wherein the pressure measuring transducer includes a measuring membrane.
20. The flowmeter of claim 18, wherein the at least one electrode body includes a first bore.
21. The flowmeter of claim 20, wherein the first bore defines a passageway forming an integrated pressure supply duct configured to convey the medium.
22. The flowmeter of claim 18, wherein the electrode body is connected terminally with a hollow body.
23. The flowmeter of claim 22, wherein a housing containing the pressure measuring transducer is connected with the hollow body by material bonding.
24. The flowmeter of claim 23, wherein the housing includes at least one contacting apparatus via which the at least one electrode assembly is electrically connected to a measuring and/or evaluation unit.
25. The flowmeter of claim 22, wherein an electrical contacting of the electrode body is implemented via the hollow body and/or a housing containing the pressure measuring transducer connected to the hollow body.
26. The flowmeter of claim 18, wherein the magnetic field generating system includes at least one coil and at least one coil core disposed in an interior of the coil, wherein the at least one coil core defines a hollow cylinder, and wherein at least one the electrode assembly is disposed within the at least one coil core.
27. The flowmeter of claim 26, wherein the at least one coil core has an interior side, and wherein insulation is disposed between the interior side and a housing containing the pressure measuring transducer connected to the hollow body.
28. The flowmeter of claim 18, wherein the electrode body includes an electrode head, wherein the electrode head has a contour.
29. The flowmeter of claim 18, wherein the electrode body comprises a fill level monitoring electrode and/or a reference electrode and/or a measuring electrode configured to sense a measurement voltage in the medium.
30. The flowmeter of claim 18, wherein the electrode body is embodied as a peg electrode, a pointed electrode or a mushroom electrode.
31. The flowmeter of claim 18, wherein the electrode body includes a first region and a second region, wherein the electrode body has in the first region a lesser thickness than in the second region, and wherein the temperature sensor is mounted in the first region on an outer surface of the electrode body.
32. The flowmeter of claim 18, wherein the temperature sensor comprises a semiconductor temperature sensor, a thermocouple, a temperature detector with quartz oscillator, a pyroelectric temperature sensor, a pyrometer or a fiber optic temperature sensor.
33. The flowmeter of claim 18, wherein the electrode head includes a measuring tube interior far, rear face, in which a cavity is defined, wherein the temperature sensor is disposed in the cavity.
34. The flowmeter of claim 18, wherein the electrode head includes an opening in which a shell containing the temperature sensor is disposed.
Description
[0065] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:
[0066] FIG. 1 a tube cross-section of a magnetic-inductive flowmeter according to the state of the art;
[0067] FIG. 2 an exploded view of an electrode assembly of the invention;
[0068] FIG. 3 a longitudinal section of a magnetic-inductive flowmeter of the invention;
[0069] FIG. 4 a cross-section of an embodiment of the invention, in which a temperature sensor is mounted flush to the electrode body;
[0070] FIG. 5 a cross-section of an additional embodiment of the invention, in which the temperature sensor is in a cavity in the electrode head; and
[0071] FIG. 6 a cross-section of an additional embodiment of the invention, in which the electrode head has a second bore, through which the temperature sensor extends.
[0072] FIG. 1 shows a conventional magnetic-inductive flowmeter. The construction and the measuring principle of magnetic-inductive flowmeters are basically known. An electrically conductive medium is conveyed through a measuring tube (1). A magnetic field producing means (7) is so arranged that its magnetic field lines extend perpendicularly to a longitudinal direction defined by the measuring tube axis. Suited as magnetic field producing means (7) is preferably a saddle coil or a pole shoe (26) with superimposed coil (23) and coil core (24). In the case of applied magnetic field, there arises in the measuring tube (1) a flow dependent potential distribution, which is sensed with two measuring electrodes (3, 4) mounted at the inner surface of the measuring tube (1). As a rule, the electrodes (3, 4) are arranged diametrically opposite one another and form an electrode axis, which extends perpendicularly to the magnetic field lines and to the longitudinal axis of the tube. Based on the measured voltage and taking into consideration the magnetic flux density, flow velocity and the tube cross-sectional area, volume flow of the medium can be determined. In order to avoid short-circuiting of the measurement voltage on the measuring electrodes (3, 4) through the tube (8), the inner surface of the tube (8) is lined with an insulating material, e.g., in the form of a plastic liner (2). The magnetic field produced by a magnetic field producing means, for example, an electromagnet, results from a direct current of alternating polarity clocked by means of an operating unit. This assures a stable zero-point and makes the measuring insensitive to influences resulting from multiphase materials, inhomogeneities in the medium or low conductivity. A measuring unit reads the voltage between the measuring electrodes (3, 4) and outputs flow velocity and/or volume flow of the medium calculated by means of an evaluation unit. Usual magnetic-inductive flowmeters have supplementally to the measuring electrodes (3, 4) two other electrodes (5, 6). On the one hand, a fill level monitoring electrode (5), which is mounted optimally at the highest point in the tube (8) and has only a minimum distance to the tube inner surface, serves to detect a partial filling of the measuring tube (1). This information is forwarded to the user and/or taken into consideration for ascertaining volume flow. Furthermore, a reference electrode (6), which is mounted usually diametrically opposite the fill level monitoring electrode (5), serves to assure a sufficient grounding of the medium.
[0073] As shown in FIG. 2, the pressure measuring transducer (12) is a part of the electrode assembly (10), which supplementally comprises at least one electrode body (11). The pressure measuring transducer (12) is, in such case, located in a housing (16), which is conductive and, thus, provides an electrical contact between electrode body (11) and a contacting apparatus (18) mounted terminally on the pressure measuring transducer (12). Thus, the entire electrode assembly (10) is in galvanic contact with the medium. In a further development, a hollow body (14) forms a hollow space (19) between the pressure measuring transducer (12) and the electrode body (11), or the outlet of the first bore (15) embodied as pressure supply duct. Thus, the pressure of the medium acting on the front end surface of the electrode body (11) is led via the pressure supply duct to the measuring membrane (13), where it is detected. Furthermore, the housing (16) is connected by material bonding with the hollow body (14). The electrode body (11) includes an electrode head (17), wherein the electrode head (17) has a contour. The contacting apparatus (18) serves for tapping the pressure of the medium converted into an electrical, or digital, signal for a measuring and/or evaluation unit (9). In such case, the contacting apparatus (18) includes at least one pin, which is in an electrical contact with the housing (16) and, thus, with the electrode body (11). The hollow body (14) is embodied in such a way that it forms, on the one hand, a hollow space (12) between measuring membrane (13) and electrode body (11) and, on the other hand, seals the electrode body (11) in such a manner that the medium flowing through the pressure supply duct cannot escape via the contact area. The electrode body (11) includes an external screw thread, which serves to secure the electrode body (11) to the measuring tube (1) and to connect to the hollow body (14), which has an internal thread.
[0074] The magnetic-inductive flowmeter shown in FIG. 3 includes an electrode assembly (10), which comprises a stylus-shaped electrode body (11) having an electrode head (17) having a contour (20), an insulating sleeve (21), a nut (22), a hollow body (14) and a pressure measuring transducer (12). The electrode body (11) includes a screw thread, which serves, on the one hand, for securing the electrode body (11) to the measuring tube (1) with a nut (22), and, on the other hand, for connecting to the hollow body (14) and/or the pressure measuring transducer (12). For mounting the electrode assembly (10) to the measuring tube (1), the electrode body (11) is led through an opening provided in the tube (8) and liner (2) and secured with an insulating sleeve (21) and a nut (22) outside of the tube. The hollow body (14) has an internal thread, such that the hollow body (14) with the shape interlocked pressure measuring transducer (12) can be screwed onto the screw thread of the electrode body (11). The hollow body (14) is embodied to produce a sealed contact to the electrode body (11), so that the medium flowing through the first bore (15) cannot escape at the contact location between the two components. The seal is preferably embodied as a conical seal. The electrode assembly (10) shown in FIG. 3 is embodied as a fill level monitoring electrode (5) and is arranged in the interior of a coil (23), especially in the interior of a coil core (24). For this further development, it is necessary to provide the coil core (24) as a hollow cylinder and to insulate the electrode assembly (10) electrically from the magnetic field producing means (7), especially the coil (23) and the coil core (24). The insulation (25) can be implemented by a coating of the inside of the coil core (24) with an electrically insulating material or by the introduction of an electrically insulating, hollow cylinder between the coil core (24) and the electrode assembly (10).
[0075] FIG. 4 shows, supplementally to the features shown in FIG. 3, a temperature sensor (28). Such is mounted flush to the electrode body (11). The tip of the temperature sensor (28) supplementally contacts the rear face of the electrode head (17). Furthermore, the electrode body (11) has two regions (I, II) with different thicknesses. The temperature sensor (28) is located in the region (I) with the lesser thickness. Such is mounted flush on the outer surface of the electrode body (11). Furthermore, the electrode body (11) includes a transition, in which the thickness gradually increases from the first region (I) until it reaches the thickness of the second region (II). In this way, a damaging of the electrical connection (33) can be avoided.
[0076] The electrode head (17) shown in FIG. 5 includes on the rear face (31) a cavity (29), into which the temperature sensor (28) extends. Thus, the temperature sensor (28) includes a first contact area, which is in contact with the outer surface of the electrode body (11) and a second contact area, which is in contact with the rear face of the electrode head (17). FIG. 5 thus shows the temperature sensor (28) partially extending into the cavity.
[0077] The electrode assembly (10) shown in FIG. 6 differs from the electrode assembly (10) shown in FIG. 5 by the feature that the electrode head (17) has an opening or perforation, especially a second bore (30), into which a shell, especially an immersion shell (32) is inserted, which has a temperature sensor (28) for measuring temperature of the medium.
[0078] FIGS. 4 to 6 all show, in each case, an insulating sleeve (21), which has a slot, through which the electrical connection (33) of the temperature sensor (28) extends.
LIST OF REFERENCE CHARACTERS
[0079] 1 measuring tube [0080] 2 liner [0081] 3 first measuring electrode [0082] 4 second measuring electrode [0083] 5 fill level monitoring electrode [0084] 6 reference electrode [0085] 7 magnetic field producing means [0086] 8 tube [0087] 9 measuring-, operating- and/or evaluation unit [0088] 10 electrode assembly [0089] 11 electrode body [0090] 12 pressure measuring transducer [0091] 13 measuring membrane [0092] 14 hollow body [0093] 15 first bore [0094] 16 housing [0095] 17 electrode head [0096] 18 contacting apparatus [0097] 19 hollow space [0098] 20 contour [0099] 21 insulating sleeve [0100] 22 nut [0101] 23 coil [0102] 24 coil core [0103] 25 insulation [0104] 26 pole shoe [0105] 27 field-guide material [0106] 28 temperature sensor [0107] 29 cavity [0108] 30 second bore [0109] 31 rear face of electrode head [0110] 32 shell [0111] 33 electrical connection [0112] I first region [0113] II second region
