JPH0618308A - Water meter detecting magnetic interference - Google Patents

Abstract

PURPOSE:To detect a mischievous act to hinder the sensing function of a rotation detecting magnetic sensor of an electronic water meter by a magnet. CONSTITUTION:When a strong magnet is brought close to a water meter to magnetically hinder the function of the water meter, one magnetic sensor for detecting the rotation of an impeller, e.g. a first magnetic sensor 1 is hindered from sensing. As a result, the output A is fixed to 'H' or 'L'. The other, second magnetic sensor 2 detects the rotation of the impeller and outputs a pulse signal B. When a second counter 5 counts a predetermined number of the pulse signals B, the counter overflows and a mischief detecting signal is generated to an output terminal 7 of an OR gate 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water meter for detecting magnetic interference caused by a mischievous magnet.

[0002]

2. Description of the Related Art An electronic water meter converts the rotation of an impeller of a metering section into an electric signal, calculates a signal pulse in an electronic circuit section, and displays an integrated value (amount of water used) on a liquid crystal display.

The rotating magnetic field of a magnet attached to the rotating shaft of the impeller is detected by two magnetic sensors provided near the rotating shaft to obtain two square waves having an electrical phase difference of 90 °, From the two signals, the rotation direction of the impeller and the rotation speed (integrated value) are calculated.

The magnet attached to the rotating shaft of the impeller is small in size, and the rotating magnetic field is weak, and this is detected by a magnetic sensor. However, there is a case where a powerful magnet is brought close to this kind of water meter to interfere with the sensing of the magnetic sensor for rotation detection, so that the amount of water used cannot be measured.

As a measure for preventing such mischief, a magnetic shield is provided to make it strong against external magnetism, and the magnetic field of the magnet caused by mischief is detected by the meter itself, and an alarm is raised to inform the meter-reading center or to the meter. To display,
It is considered to make it clear at the time of meter reading.

[0006]

However, in order to detect the magnetic field of the magnet due to mischief, a mischief detection sensor other than the two magnetic sensors for detecting the rotating magnetic field is provided. This other mischief detection sensor cannot be placed at the same position as the two rotation detection magnetic sensors, and cannot directly detect the magnetic field of the mischief magnet applied to the two rotation detection magnetic sensors. However, depending on the direction of the magnet, one separate sensor cannot detect the magnetic field for mischief, and it requires two or more different sensors for mischief detection.
There was also the problem of high costs.

Therefore, an object of the present invention is to solve the above problems and provide an electronic water meter capable of detecting magnetic interference.

[0008]

In order to achieve the above object, the present invention detects the rotating magnetic field of a magnet attached to an impeller and generates electric pulse signals electrically different in phase by 90 ° from each other. In the electronic water meter having the first magnetic sensor and the second magnetic sensor, the output of one magnetic sensor is fixed to "H" or "L", and the output of the other magnetic sensor is input with a constant pulse. Then, a mischief detection circuit for recognizing and outputting the mischief is provided.

[0009]

Since the direction of the magnetic field is one in the obstruction magnetism caused by the mischievous magnet, the sensing of the first and second magnetic sensors for detecting the rotation of the impeller of the electronic water meter is obstructed at the same time. Is difficult, and if only one of them interferes, the meter's integrated display stops, so the disturber cannot confirm that both sensors are disturbing. Therefore, in general, only one of the magnetic sensors receives the sensing interference, and its output remains fixed at "H" or "L". The other magnetic sensor outputs the electric pulse signal normally to some extent. However, in this state, the meter itself becomes defective in integration, and the amount of water used cannot be measured.

If this state is continued and the output of the other magnetic sensor is output as a constant pulse, it can be seen that the player is mischievous.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of FIG. 1, 1 and 2 are first and second magnetic sensors for sensing a rotating magnetic field of a magnet attached to an impeller (not shown) of an electronic water meter,
It outputs electrical pulse signals that are 90 degrees out of phase electrically.

FIG. 2 shows this output pulse signal.
Are rotation detection signals output from the first and second magnetic sensors, respectively, and have electrical angles deviated from each other by 90 °. Referring again to FIG. 1, reference numeral 3 denotes a mischief detection circuit, which has a first counter 4, a second counter 5, an OR gate 6, and an output terminal 7.

The output A of the first magnetic sensor 1 is input to the clock terminal CK of the first counter and the reset terminal R of the second counter 5. The output B of the second magnetic sensor 2 is input to the clock terminal CK of the second counter 5 and the reset terminal R of the first counter 4.

Each of the counters 4 and 5 is configured to be reset at the edge of the output pulse signal B or A of the second or first magnetic sensor input to the reset terminal R thereof. The carry output from each carry-out terminal CO of both counters 4 and 5 is input to the OR gate 6, and the output of the OR gate 6 is connected to the output terminal 7 of the mischief detection circuit 3.

Now, when there is no mischief caused by the magnet, the impeller of the water meter rotates, and the rotating magnetic field of the magnet attached to the impeller is normally sensed by both magnetic sensors 1 and 2, then From the second magnetic sensors 1 and 2, the output pulse signals indicated by A and B in FIG.
Are input to the clock terminals CK of the counters 4 and 5 of
At the same time, the output pulse signals A and B are input to the reset terminals R of the second and first counters 4 and 5, respectively,
Both counters do not count up.

However, when a mischief is caused by a strong magnetic force, the sensing of either one of the magnetic sensors 1 or 2 is disturbed and only the other magnetic sensor outputs an output pulse signal. For example, only the first magnetic sensor 1 is prevented from sensing and its output is fixed at "H" or "L", and only the second magnetic sensor 2 outputs the output pulse signal B.
Is continuously output.

Then, the first counter 4 does not count up, the output pulse signal B is continuously input to the clock terminal CK of the second counter 5, and the reset terminal R resets from the first magnetic sensor. Since no signal is input, when the constant output pulse signal B is counted, the second counter 5 overflows, a carry is output from the carry-out terminal CO, is input to the OR gate 6, and a mischief detection signal is output to the output terminal 7. Is output.

In this manner, the mischief caused by the magnet is detected by using both the magnetic sensors 1 and 2 for rotation detection which are originally used. Contrary to the above description, when the second magnetic sensor 2 loses the sensing function and only the first magnetic sensor 1 detects rotation, the second counter 5 counts up with a similar operation. When the first counter 4 counts the output pulse signal A from the first magnetic sensor 1 by a certain number, it overflows, a carry is output, and a mischief detection signal is output to the output terminal 7.

The first and second magnetic sensors 1 and 2 are
However, if the sensing function is disturbed at the same time by the mischief of a strong magnet, and the output of the electromagnetic sensor is constant at "H" or "L", the mischief cannot be detected. For the reason, it is not possible, so there is no need to think about measures.

[0020]

As described above, the water meter for detecting magnetic interference of the present invention utilizes the two magnetic sensors for rotation detection which are originally provided in the electronic water meter, and the magnetic sensor itself is used. Since the magnetism due to such mischief is detected, no special magnetic sensor is required for the mischief detection, the cost can be prevented from being high, and the magnetism due to the mischief to the rotation detection magnetic sensor is directly detected, so that the mischief detection can be surely performed. is there.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of the present invention.

FIG. 2 is a waveform diagram of an output pulse signal of the magnetic sensor.

[Explanation of symbols]

 1 1st magnetic sensor 2 2nd magnetic sensor 3 Mischief detection circuit

Claims (1)

[Claims] 1. An electronic device having a first magnetic sensor and a second magnetic sensor, which detect a rotating magnetic field of a magnet attached to an impeller and generate electric pulse signals electrically different in phase from each other by 90 °. In the water meter, the output of one magnetic sensor is fixed to "H" or "L" and the output of the other magnetic sensor is provided with a mischief detection circuit that recognizes and outputs the mischief when a constant pulse is input. A water meter that detects magnetic interference.