Patent Application
20220074769
Magnetic inductive flow meters are used for determining the flow speed and/or the volume flow of a medium in a measurement tube. A magnetic inductive flow sensor comprises a magnetic-field-generating device that generates a magnetic field perpendicular to the transverse axis of the measurement tube. Single or multiple coils are typically used for this purpose. In order to realize a predominantly homogeneous magnetic field, pole shoes are additionally shaped and mounted in such a manner that an axis of symmetry of the magnetic field lines extends substantially perpendicularly to the transverse axis. A pair of measuring electrodes mounted on the lateral surface of the measurement tube taps an inductively generated electrical measuring voltage, which arises if a conductive medium flows in the direction of the longitudinal axis when the magnetic field is applied. Since, according to Faraday's law of induction, the tapped measuring voltage depends on the speed of the flowing medium, the flow speed and, with the aid of a known tube cross-section, the volume flow of the medium can be determined from the measuring voltage.
In contrast to magnetic inductive flow meters, in which a coil arrangement for generating a magnetic field penetrating a measurement tube is fixed on the lateral surface of the measurement tube and at least two measuring electrodes are situated in the inner wall, magnetic inductive flow sensors are inserted with their typically circular cylindrical housing into a lateral opening of the measurement tube and fixed in a fluid-tight manner. The mentioned coil arrangement on the lateral surface of the measurement tube is dispensed with since the magnetic field only exists in the region of the front end of the flow sensor projecting into the medium or is generated by a current flowing through its coil arrangement in such region. The flow sensor typically comprises two pin-shaped measuring electrodes. However, EP0534003A1 also discloses flow sensors having a pin-shaped measuring electrode situated in the center of the front end and a ring electrode surrounding the pin-shaped measuring electrode.
EP0892251A1 discloses a magnetic inductive flow sensor, whose front end projecting into the medium takes the form of a spherical cap and in which a first and a second galvanic electrode are situated on one of the meridians of the spherical cap in a manner symmetrical to an apex of the meridian. The flow sensor is to be immersed practically perpendicularly to a longitudinal axis of the conduit and is to be aligned by rotation in such a manner that a line connecting the two electrodes extends perpendicularly to the direction of flow.
A filling level monitoring system with an electrode for monitoring the filling level of a flowing medium in a tube is known from DE102012109308A1, which electrode has an integrated temperature sensor so that, in addition to the flow volume, the flow speed and the filling level, the temperature of the medium can also be monitored.
EP0770855A1 already discloses a magnetic inductive flow meter that, in addition to the measuring electrodes for determining a flow speed, has two pressure transducers that are situated in the wall of the measurement tube along a surface line.
U.S. Pat. No. 5,670,724 teaches a flow meter having a pair of measuring electrodes and a pressure transducer situated directly between the two measuring electrodes.
However, such embodiments are disadvantageous in that an additional opening has to be incorporated into the measurement tube for the installation of the pressure transducer and/or of the temperature sensor at the measurement point. However, each opening is a potential leakage point and should thus be avoided as much as possible.
The invention is based on the object of providing a magnetic inductive flow sensor, which is configured to determine an additional process parameter of the medium in addition to the flow volume and/or the flow speed.
The task is achieved by the flow sensor according to claim 1 and the measurement point according to claim 8.
The magnetic inductive flow sensor according to the invention for determining the flow volume and/or the flow speed of a liquid medium in a measurement tube comprises a housing, a front part situated in the end of the housing and having a front end, wherein the front end can be loaded by the medium, at least two measuring electrodes forming a galvanic contact with the medium and a magnetic-field-generating device situated in the housing for generating a magnetic field extending through the front end, and is characterized in that at least one sensor for determining a process parameter of the medium is situated in the housing.
It is particularly advantageous if at least one sensor is installed in the housing of the magnetic inductive flow sensor. For this purpose, the magnetic-field-generating device and the front part are adapted in such a manner that the sensor can be accommodated in the interior of the housing, without having to increase the outer diameter of the commercially available housing. By integrating the sensor into the housing of the flow sensor, no further opening in the conduit is required. The housing of the magnetic inductive flow sensor is typically designed to be circular-cylindrical, as a result of which it can easily be introduced into a laterally mounted opening of an existing conduit.
A sensor for determining a process parameter of the medium comprises a filling level meter, pressure transducer, temperature sensor, pH sensor, density sensor and/or viscometer.
In accordance with one embodiment, the sensor comprises a pressure transducer and/or a temperature sensor, wherein the pressure acting on the front end can be applied to the pressure transducer, wherein the temperature sensor is configured to determine a measurement signal dependent on the medium temperature.
The temperature sensor comprises a semiconductor temperature sensor, a thermocouple, a quartz oscillator temperature sensor, a pyroelectric temperature sensor, a pyrometer or a fiber optic temperature sensor.
The pressure transducer can be designed arbitrarily. The pressure transducer can be designed, for example, as a strain gauge, piezoresistive pressure sensor, piezoelectric pressure sensor, capacitive pressure sensor, inductive pressure sensor, optical pressure sensor, thermal pressure sensor or Hall pressure sensor.
In accordance with one embodiment, the front end of the pressure transducer projects from the front end of the front part. The medium flowing to the front end also contacts the pressure transducer. Alternatively, the front part has a recess into which the pressure transducer is inserted in such a manner that the front end of the pressure transducer is sunk in the recess. In both cases, the medium pressure acts directly on the pressure transducer, without it having to be conducted through a differential pressure channel to the pressure transducer.
In accordance with another embodiment, the pressure transducer is integrated in the housing and separated from the interior of the conduit by an intermediate part, a differential pressure channel or air inclusions.
The temperature sensor is configured to determine a measurement signal dependent on the medium temperature. For this purpose, it is advantageous if the temperature sensor contacts the medium.
In accordance with an alternative embodiment, the temperature sensor does not contact the medium but rather is in contact with the front part or with the housing and thus determines the measurement signal dependent on the medium temperature. Therefore, the part of the front part with which the temperature sensor is in contact is ideally made of a material having sufficiently good thermal conductivity.
In accordance with one embodiment, two sensors are situated in the housing. It is particularly advantageous if two sensors, especially, the pressure transducer and the temperature sensor, are accommodated in the housing. This makes it possible to dispense with the incorporation of additional openings into the conduit. In accordance with one embodiment, a disk with at least one differential pressure channel is situated between the pressure transducer and the front end.
It is particularly advantageous if a disk having at least one differential pressure channel is inserted between the pressure transducer and the front end of the flow sensor. The medium can thereby be conducted in a manner centered onto the pressure transducer, for example a measuring membrane. Furthermore, the pressure transducer is thereby not directly exposed to the medium at the front end. The disk advantageously decouples the pressure transducer from the medium so that pressure fluctuations in the medium are absorbed by the disk before they reach the pressure transducer.
The connection of the pressure transducer is ideally situated in the interior of the housing, where it is connected to the measuring and/or evaluating unit.
In accordance with one embodiment, the front part has at least a first and a second opening for the measuring electrodes and a third opening for the temperature sensor.
It is advantageous if the front part has an opening for the temperature sensor so that the temperature sensor can be attached in a fluid-tight manner in the front part and has direct contact with the medium. The connection of the temperature sensor is ideally situated in the interior of the housing, where it is connected to the measuring and/or evaluating unit.
In accordance with one embodiment, the front part has at least one, preferably three, openings, each designed as a differential pressure channel.
It is particularly advantageous if the front part has at least one and preferably three openings, each designed as a differential pressure channel, and thus conducts the medium to the pressure transducer situated in the housing. As a result, the pressure transducer is not in direct contact with the medium at the front end. The diameter of the openings is advantageously adapted in such a manner that particles from the medium are prevented from reaching the pressure transducer or damaging the pressure transducer or parts of the pressure transducer. This is particularly advantageous in the drinking water sector since damage to, for example, the measuring membrane and penetration of, for example, oil from the piezoresistive pressure transducer can thus be prevented.
In accordance with one embodiment, the pressure transducer comprises a printed circuit board with connections for the temperature sensor and/or the pressure transducer and at least the measuring electrodes, wherein the printed circuit board is connected to a measuring and evaluating unit.
It is particularly advantageous if the printed circuit board has a serial data bus, especially, an I2C data bus, and is subordinate to the I2C protocol. As a result, the measuring electrodes, the temperature sensor and/or the pressure transducer can be connected to the measuring and/or evaluating unit in a simple and cost-effective manner via the data bus.
A measurement point according to the invention for determining the flow of a medium comprises a conduit with a wall for guiding the medium and an opening in the wall and is characterized in that a flow sensor according to one of the preceding claims is inserted through the opening into the conduit.
The invention is explained in greater detail with reference to the following figures. The following are shown:
The measuring principle on which the invention is based is first explained on the basis of the perspective and partially cut illustration of
The close-up view shows two recesses in the front part (22). A first recess serves as a socket for the pressure transducer (19). A second, circular cylindrical recess serves as a socket for the coil core and is designed to guide and hold in a positive-locking manner the first part of the circular cylindrical coil core. For this purpose, the diameter of the recess is adapted to the diameter of the first part of the coil core (7). As a result, the end of the coil core terminates at or near the front end (26) and the magnetic field lines exiting the front end (26) extend or the axis of symmetry of the magnetic field lines extends substantially perpendicularly through the front end (26).
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 132 885.0 | Dec 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/082013 | 11/21/2019 | WO | 00 |
