JP2005292011A - Electromagnetic log sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a flow path for taking in water that resists the traveling direction of a ship in an electromagnetic log sensor, arrange a non-contact type detection electrode in the flow path, and surround the flow path with the same potential, An electromagnetic log sensor in which noise due to a potential difference from the outside does not occur is provided.
An electromagnetic log sensor includes a pair of flow paths that can take in water that resists the traveling direction of a ship, an excitation coil that generates a magnetic field for the pair of flow paths, and each of the pair of flow paths. A detection electrode disposed in an insulated state, and a guard electrode disposed so as to surround the flow channel in each of the pair of flow channels and spaced apart from the detection electrode by a predetermined interval. .
[Selection] Figure 1

Description

  The present invention relates to an electromagnetic log sensor, and more particularly to an electromagnetic log sensor that measures a navigation speed of a ship.

The electromagnetic log sensor in the prior art is used as a navigation speedometer for a ship, and as shown in FIGS. 8 and 9, a casing 110 formed in a cylindrical shape is penetrated through the bottom of the ship and its tip is projected into water. To do. A coil 112 wound around a core 111 and a pair of electrodes 113a and 113b on the left and right with respect to the traveling direction of the ship are arranged at the tip of the electromagnetic log sensor.
When the exciting current io is passed through the coil 112, the ship moves along the traveling direction indicated by the arrow shown in FIG. 9 when the magnetic field Φ exists in the water. Then, an electromotive force eo is detected from the electrodes 113a and 113b. When water (seawater) is considered as a conductor, this applies Faraday's law of electromagnetic induction, in which an electromotive force is generated in a conductor moving in a magnetic field.
Thus, when the intensity of the magnetic field Φ is constant, a speed signal (electromotive force) having a magnitude proportional to the relative speed between the ship bottom and water is detected from the electrodes 113a and 113b.

Japanese Patent Laid-Open No. 11-23310 (pages 2 to 3 and FIG. 2)

However, in the electromagnetic log sensor described in the prior art, there is an electrode at the tip, and this electrode is in direct contact with water (seawater). There is a problem that arises.
In addition, in order to prevent such fluctuations in output, there is a problem that maintenance work for removing deposits on the tip including the electrode must be performed periodically.
Furthermore, since the electrode is in direct contact with water (seawater), there is a problem that noise is generated due to contact with the fluid floating substance even if the electrode is not fouled.

  Therefore, there is a problem that an electromagnetic log sensor that does not generate noise due to contact with a fluid floating substance without causing fluctuations in output due to electrode fouling, without requiring regular maintenance work, has to be solved.

In order to solve the above problems, the electromagnetic log sensor of the present invention is configured as follows.
(1) The electromagnetic log sensor includes a pair of flow paths that can take in water that resists the traveling direction of the ship, an excitation coil that generates a magnetic field for the pair of flow paths, and each of the pair of flow paths. A detection electrode disposed in an insulated state, and a guard electrode disposed so as to surround the flow path in each of the pair of flow paths and spaced apart from the detection electrode by a predetermined interval.
(2) The electromagnetic log sensor according to (1), wherein a signal detected by the detection electrode is amplified and the amplified signal is fed back and applied to the guard electrode.
(3) The electromagnetic log sensor according to (1), wherein the exciting coil is provided at a position between the pair of flow paths.
(4) The electromagnetic log sensor according to (1), wherein the pair of flow paths are formed in a semi-cylindrical shape, and the straight portions thereof are formed back to back.

(5) The electromagnetic log sensor includes a pair of detection electrodes arranged in an insulated state on the inner side walls on both sides through which water passes with respect to the traveling direction of the ship, and an excitation coil that generates a magnetic field at a position sandwiching the pair of detection electrodes And a guard electrode disposed at a predetermined interval so as to cover each of the pair of detection electrodes.
(6) The electromagnetic log sensor according to (5), wherein a signal detected by the detection electrode is amplified and the amplified signal is fed back and applied to the guard electrode.

  The electromagnetic log sensor of the present invention is not affected by adhesion of an insulator because the detection electrode is a non-contact type, and surrounds the fluid to be measured at the same potential, so that noise due to a potential difference from the outside does not occur. There is an effect.

  The electromagnetic log sensor according to the first embodiment of the present invention will be described below in detail with reference to the drawings.

  As shown in FIGS. 1 to 4, the electromagnetic log sensor according to the first embodiment of the present invention has a semi-cylindrical shape for taking in water that resists the traveling direction of the ship (see FIG. 2) on both sides of the casing 11. Forming a pair of flow paths 12a, 12b whose straight portions are back-to-back, and arranging an excitation coil 17 in which a coil 16 is wound around an iron core 15 at a central position sandwiching the pair of flow paths 12a, 12b, The detection electrodes 13a and 13b are provided at positions insulated from the respective flow paths 12a and 12b. Further, outside the detection electrodes 13a and 13b, guard electrodes 14a and 14b that cover the whole of the detection electrodes 13a and 13b and maintain insulation from the detection electrodes 13a and 13b so as to cover the flow paths 12a and 12b. Is arranged. Each of the pair of flow paths 12a and 12b is provided with ground electrodes 18a and 18b for detecting a reference potential. The ground electrodes 18a and 18b may be either a wetted type or a non-wetted type. In the embodiment, the grounded electrodes 18a and 18b have a non-wetted type structure.

As shown in FIG. 4, the detection electrodes 13a and 13b are connected to the non-inverting input terminals (+) of the preamplifiers 19a and 19b having high input impedance, respectively, and the inverting input terminals (−) are respectively connected to the guard electrodes 14a and 14b. And connected to the output terminals of these preamplifiers 19a and 19b. The output terminals of the preamplifiers 19a and 19b are connected to the input terminal of the differential amplifier 20, respectively.
As described above, the guard electrodes 14a and 14b are configured to amplify the signals detected by the detection electrodes 13a and 13b by the preamplifiers 19a and 19b, and apply the amplified signals as feedback.

  In the electromagnetic log sensor having such a configuration, when the excitation coil 17 is excited, a magnetic field is generated in the vicinity of the detection electrodes 13a and 13b, so that the ship sails in the ship traveling direction shown in FIG. 2 and the pair of flow paths 12a and 12b. The electromotive force excited by the flow of water (seawater) is detected by the detection electrodes 13a and 13b provided in the pair of flow paths 12a and 12b, respectively. Non-wetted capacitive electrodes are used as the detection electrodes 13a and 13b. The detection target fluid is surrounded by the detection electrodes 13a and 13b of the pair of flow paths 12a and 12b and the guard electrodes 14a and 14b having the same potential. Surrounding with electric potential can prevent external noise.

  Next, an electromagnetic log sensor according to a second embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 5 to 7, the electromagnetic log sensor of the second embodiment is formed in a cylindrical casing 11 </ b> A, and is water with respect to the casing 11 </ b> A in the traveling direction of the ship (see FIG. 6). A pair of detection electrodes 13c, 13d arranged in an insulated state on the inner side walls on both sides through which the coil passes, and an excitation coil 17 comprising an iron core 15 and a coil 16 that generates a magnetic field at a position sandwiching the pair of detection electrodes 13c, 13d, The guard electrodes 14c and 14d are arranged with a predetermined interval so as to cover the whole of the pair of detection electrodes 13c and 13d.

  And each of the side wall surface through which water (seawater) flows is provided with ground electrodes 18c and 18d for detecting a reference potential. The earth electrodes 18c and 18d may be either a wetted type or a non-wetted type. In the embodiment, the ground electrodes 18c and 18d have a non-wetted type structure.

As shown in FIG. 7, the detection electrodes 13c and 13d are connected to non-inverting input terminals (+) of preamplifiers 19a and 19b having high input impedances, respectively, and the inverting input terminals (−) are guard electrodes 14c and 14d, respectively. And connected to the output terminals of these preamplifiers 19a and 19b. The output terminals of the preamplifiers 19a and 19b are connected to the input terminal of the differential amplifier 20, respectively.
As described above, the guard electrodes 14c and 14d are configured to amplify the signals detected by the detection electrodes 13c and 13d by the preamplifiers 19a and 19b, and apply the amplified signals as feedback.

  In the electromagnetic log sensor having such a configuration, when the exciting coil 17 is excited, a magnetic field is generated in the vicinity of the detection electrodes 13c and 13d, so that the ship sails in the ship traveling direction shown in FIG. The electromotive force excited by the flow of water (seawater) is detected by the detection electrodes 13c and 13d provided on both wall surfaces. The detection electrodes 13c and 13d are non-wetted capacitive electrodes, and are surrounded by a pair of detection electrodes 13c and 13d and guard electrodes 14c and 14d having the same potential to detect the fluid to be measured in the same potential state. External noise can be prevented.

  In the electromagnetic log sensor, a flow path for taking in water that resists the traveling direction of the ship is formed, a non-contact type detection electrode is arranged in the flow path, and the periphery of the flow path is surrounded by the same potential. An electromagnetic log sensor that does not generate noise due to a potential difference is provided.

It is explanatory drawing which showed the sensor part among the electromagnetic log sensors of 1st Example of this invention. It is a top view of a sensor same as the above. It is explanatory drawing which expanded and showed the sensor part partially same as the above. It is explanatory drawing of the electromagnetic log sensor containing a circuit similarly. It is explanatory drawing which showed the sensor part among the electromagnetic log sensors of 2nd Example of this invention. It is a top view of a sensor same as the above. It is explanatory drawing of the electromagnetic log sensor containing a circuit similarly. It is explanatory drawing which shows the electromagnetic log sensor in a prior art. It is a top view of a sensor same as the above.

Explanation of symbols

11 Case 11A Case 12a Flow path 12b Flow path 13a Detection electrode 13b Detection electrode 13c Detection electrode 13d Detection electrode 14a Guard electrode 14b Guard electrode 14c Guard electrode 14d Guard electrode 15 Iron core 16 Coil 17 Excitation coil 18a Earth electrode 18b Earth electrode 18c Ground electrode 18d Ground electrode 19a Preamplifier 19b Preamplifier 20 Differential amplifier.

Claims (6)

A pair of channels that can take in water that resists the direction of travel of the ship;
An exciting coil that generates a magnetic field for the pair of flow paths;
A detection electrode disposed in an insulated state in each of the pair of flow paths;
A guard electrode disposed in a state of surrounding the flow path in each of the pair of flow paths and separated by a predetermined interval around the detection electrode;
An electromagnetic log sensor comprising:   The electromagnetic log sensor according to claim 1, wherein a signal detected by the detection electrode is amplified to the guard electrode, and the amplified signal is fed back and applied.   The electromagnetic log sensor according to claim 1, wherein the exciting coil is provided at a position between the pair of flow paths.   The electromagnetic log sensor according to claim 1, wherein the pair of flow paths are formed in a semi-cylindrical shape, and the straight portions thereof are formed back to back. A pair of detection electrodes arranged in an insulated state on the inner side walls on both sides where water passes with respect to the traveling direction of the ship;
An exciting coil that generates a magnetic field at a position between the pair of detection electrodes;
A guard electrode disposed at a predetermined interval so as to cover each of the pair of detection electrodes;
An electromagnetic log sensor comprising: 6. The electromagnetic log sensor according to claim 5, wherein a signal detected by the detection electrode is amplified to the guard electrode, and the amplified signal is fed back and applied.

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