JP3396906B2 - Flow measurement device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring an integrated value of the amount of gas, water, electricity, etc. used by a gas meter, a water meter, an electric power meter or the like and sucking the integrated value into a data collecting device. It is about.

[0002]

2. Description of the Related Art In recent years, a so-called automatic meter reading system has been introduced which absorbs an integrated value measured by a meter from a remote place using a telephone line or the like. In addition, it has been attempted to connect the telephone line and the meter by a wireless line. 6A and 6B are block diagrams of an automatic meter-reading system using a conventional flow rate measuring device, which will be described. In FIG. 6A, 1 is a gas pipe connected to a home, 2 is a gas pipe 1
A gas flow meter (so-called gas meter) that is provided on the way to measure the amount of gas used in the target household, 3 is a storage means, and 4 is a voltage controlled oscillator (hereinafter referred to as VCO: Voltage Co).
(referred to as "ntrolled oscillator"), 5 is a transmitting means, 6 is a controlling means, 7 is a receiving means, and 8 is an antenna. Receiving means 7
Is composed of amplification means 8, mixing means 9, oscillation means 10, amplification means 11, mixing means 12, oscillation means 13, amplification means 14, and demodulation means 15. In FIG. 6B, reference numeral 16 is a public telephone line, and 17 is a no-ringing network control means (hereinafter T-NCU :) connected to the public telephone line 16.
Terminal-Network Control Unit), 18 is an interface means, 19 is a voltage controlled oscillator (hereinafter VC)
O: Voltage Controlled Oscillator), 20 is transmitting means, 21 is control means, 22 is receiving means, and 23 is an antenna. The receiving means 22 comprises an amplifying means 24, a mixing means 25, an oscillating means 26, an amplifying means 27, a mixing means 28, an oscillating means 29, an amplifying means 30, and a demodulating means 31. A management device (not shown in FIG. 6) for managing the meter reading data is connected to the telephone line 16 and calls the T-NCU 17 via the telephone line 16. The called T-NCU 17 outputs a meter reading data request signal to the interface unit 18. The interface unit 18 converts the input meter reading data request signal into a level and a waveform and outputs V.
Output to CO19. In the VCO 19, the oscillation signal is frequency-modulated by the meter reading data request signal. The signal frequency-modulated by the VCO 19 is amplified by the transmitting means 20 and radiated as a radio wave from the antenna 23 into the space. The radiated radio wave is, for example, a radio wave in the 400 MHz band, which has been approved for use as a low power radio in recent years. The radio wave radiated from the antenna 23 is received by the antenna 8 and guided to the amplification means 8. The amplifying means 8 amplifies the received signal in the 400 MHz band, and the mixing means 9 multiplies the signal from the oscillating means 10 to frequency-convert it into a signal in the 20 MHz band. Of the frequency-converted received signal, only the signal in the vicinity of the desired signal is selectively amplified by the amplifying means 11, and further mixed with the signal from the oscillating means 13 in the mixing means 12 to be frequency-converted into a 455 kHz signal. The reception signal frequency-converted to 455 kHz is amplified by the amplifying means 14 after passing through a filter having a narrow band centering on 455 kHz. Then, the demodulation means 15 detects the frequency and outputs a meter reading data request signal from the demodulation means 15. The storage unit 3 stores the integrated value of the gas flow rate measured by the gas flow meter 2. When the control means 6 receives the meter reading data request signal, the control means 6 activates the storage means 3 and the transmission means 5. Then, the oscillation signal of the VCO 4 is frequency-modulated by the integrated data stored in the storage means 3, and the frequency-modulated signal is amplified by the transmission means 5 and is radiated as a radio wave into the space from the antenna 8. The frequency of the radio wave radiated from the antenna 8 is the same as the frequency of the radio wave radiated from the antenna 23. The radio wave frequency-modulated by the integrated data is received by the antenna 23 and guided to the amplification means 24. The amplifying means 24 amplifies the received signal in the 400 MHz band, and the mixing means 25 multiplies it with the signal from the oscillating means 26.
Converts frequency to MHz band signal. In the frequency-converted received signal, only the signal in the vicinity of the desired signal is selectively amplified by the amplification means 27, and the mixing means 28 further oscillates the oscillation means 2.
The signal from 9 is multiplied and the frequency is converted to a signal of 455 kHz. The reception signal frequency-converted to 455 kHz is amplified by the amplifying means 30 after passing through a filter having a narrow band centering on 455 kHz. Then, the demodulation means 31 frequency-detects and the integrated data is output from the demodulation means 31. When the control means 21 receives the integrated data, it activates the transmitting means 20 to send a response signal to the gas flow meter indicating that the integrated data has been received via the antenna 23, and at the same time, via the interface 18, T-.
The NCU 17 is activated and the integrated data is sent to the telephone line 16.

[0003]

However, the above conventional structure has the following problems.

(1) The flow rate measuring device installed outside has severe environmental conditions such as temperature, and is required to have high reliability against a temperature change of -30 ° C to 70 ° C. In particular, it is necessary to collect the meter-reading data without fail because a fee is collected from the gas user based on the meter-reading data. However V
Since it has many oscillators such as CO4 or 19, oscillating means 10 or 26, oscillating means 13 or 29, it is difficult to suppress the fluctuation of the oscillating frequency due to the temperature of all the oscillators to a certain value or less. .

(2) In the flow meter, the flow path portion for measuring the flow rate occupies a large volume weight, and therefore a device for construction is required to mount the electric circuit portion. However, 400MHz band amplification means 8 and 24, 20MHz
Band amplification means 11 and 27, 455 kHz amplification means 14
And 30 each require a band-pass filter having a narrow band and steep attenuation characteristics. As the band-pass filter, a mechanical filter utilizing the mechanical vibration characteristics of crystal or ceramic is used. Therefore, the shape of the electric circuit portion becomes large and it is difficult to mount.

Further, the amplification means 11 or 2 for the 20 MHz band
The high-frequency signal of a small level must be amplified with a large amplification degree by the amplifying means 14 or 30 of 7, or 455 kHz. Therefore, great care must be taken in mounting the high-frequency circuit, which is a very difficult task for the assembler of the flow meter that cannot be a high-frequency circuit.

The present invention solves the above problems, and an object of the present invention is to realize a flow rate measuring device which can collect meter reading data with high reliability even in a severe environment of use and is easy to manufacture. It is what

[0008]

In order to achieve the above object, a flow rate measuring device of the present invention comprises a storage means for measuring and storing measurement data of a flow meter, and the measurement data from the storage means into a carrier signal. Transmission means for carrying and transmitting, reception means for receiving a request signal requesting transmission of measurement data from the storage means or a response signal to the measurement data, and reception for detecting the level of a reception signal received by the reception means Level detection means, reception level adjustment means for adjusting the reception signal level received by the reception means, and one of a plurality of predetermined output signals corresponding to the reception level from the reception level detection means A reception level control means for outputting to the reception level adjustment means to control the reception level; and an activation terminal for activating the reception level control means, The receiving means includes an oscillating means that oscillates at a frequency close to a carrier signal frequency to be received, a first mixing means that extracts a difference signal between the signal from the oscillating means and the received signal, and a phase shift of the signal from the oscillating means. Second mixing means for extracting a difference signal between the received signal and the received signal, and a phase difference detecting means for detecting a phase difference between the signal from the first mixing means and the signal from the second mixing means, A frequency correction means is provided for detecting a difference between the frequency of the carrier signal to be received and the signal frequency from the oscillating means, and controlling the oscillating frequency of the oscillating means in the direction of eliminating the frequency difference.

[0009]

According to the present invention, since the number of oscillators can be reduced and the number of high frequency amplification stages can be reduced by the above configuration, meter reading data can be collected with high reliability even in a harsh operating environment, and A flow rate measuring device that is easy to manufacture can be realized.

[0010]

Embodiments of the present invention will be described below with reference to FIGS. The same functional blocks as those in the conventional example of FIG. 6 are given the same numbers. In FIG. 1, 1 is a gas pipe connected to a home, 2 is a gas flow meter (so-called gas meter) provided in the middle of the gas pipe 1 for measuring the amount of gas used in the target home, 3 is a storage means, 32 is VC
Reference numerals O and 5 are transmission means, 6 is control means, 7 is reception means, 8 is an antenna, 43 is reception level detection means, and 44 is reception level control means. The reception means 7 includes reception level adjustment means 33, mixing means 34 and 35, 90 ° phase shifter 36, low pass filters 37 and 38 for removing adjacent channel signals, low frequency amplification means 39 and 40, phase difference detection means. 41 and frequency correction means 42. The VCO 32 is also a part of the receiving means 7. Figure 2
16 is a public telephone line, 17 is a public telephone line 16
Connected to the T-NCU, 18 is interface means, 45 is VCO, 20 is transmission means, 21 is control means,
22 is a receiving means, 23 is an antenna, 56 is a receiving level detecting means, and 57 is a receiving level control means. Receiving means 2
2 is a reception level adjusting means 46, mixing means 48 and 49, 90 ° phase shifter 47, low pass filters 50 and 51 for removing adjacent channel signals, low frequency amplifying means 52 and 53, phase difference detecting means 54, It is composed of frequency correction means 55. The VCO 45 is also a part of the receiving means 22. A management device (not shown in FIG. 2) for managing the meter reading data is connected to the telephone line 16 and calls the T-NCU 17 via the telephone line 16. The called T-NCU 17 outputs a meter reading data request signal to the interface unit 18. Interface means 18
Converts the level and the waveform of the input meter reading data request signal and outputs the converted signal to the VCO 45. In the VCO 45, the oscillation signal is frequency-modulated by the meter reading data request signal. VCO45
The signal frequency-modulated by is amplified by the transmitting means 20 and is radiated into the space as a radio wave from the antenna 23. The radiated radio wave is, for example, a radio wave in the 400 MHz band, which has been approved for use as a low power radio in recent years. Antenna 23
The radiated radio wave is received by the antenna 8 and guided to the reception level adjusting means 33. The reception level adjusting means 33 amplifies or attenuates the reception signal in the 400 MHz band. Now, S = cos {ω + p (t) * △ ω} * tp (t): 1 or -1 on the antenna 8.
Consider the case where the FSK signal S represented by the code sequence ω: Carrier wave angular frequency Δω: Angular frequency deviation is input. The FSK signal S is input to the mixing means 34 and 35. The VCO 32 generates a signal Q represented by Q = COS {ω + x} * tx: oscillation angular frequency error from the carrier angular frequency ω. 90 ° phase shifter 3
In 6, the signal Q from the VCO 32 is phase-shifted by 90 ° and Q ′ = SIN {ω + x} t. In the mixing means 34, VC
The signal Q from O32 and the FSK signal S are multiplied. In the mixing means 35, the signal Q ′ from the 90 ° phase shifter 36 and the FSK signal are multiplied. Then, high-frequency components other than the desired signal are removed by the low-pass filters 37 and 38, and the desired signal is amplified by the low-frequency amplification means 39 and 40. Therefore, the following signals are output to the terminals a and b.

Terminal a: S * Q = COS {p (t) * Δω−x} * t Terminal b: S * Q ′ = SIN {p (t) * Δω−x} * t Frequency correction means 39 Then, when an additional signal transmitted prior to the code string having information is received, the above-mentioned angular frequency error x
A signal for controlling the VCO 32 is output in the direction of zero. The following description will be given assuming x = 0. The relationship between the code sequence p (t) and the signal waveforms of the terminals a, b and c is shown in FIG. 3 and will be described with reference to FIG. As is apparent from FIG. 3, when the code string p (t) is -1, the signal at the terminal b leads the signal at the terminal a by 90 ° in phase. On the other hand, when the code string p (t) is 1, the terminal a
The phase of the signal at the terminal b is delayed by 90 ° with respect to the signal of.
Therefore, by detecting the phase difference between the signal at the terminal a and the signal at the terminal b in the phase difference detecting means 41, the original code string p
(t) can be reproduced and the original code string p (t) can be output from the terminal c. The code string p (t) output from the terminal c
Is a meter reading data request signal. The storage unit 3 stores the integrated value of the gas flow rate measured by the gas flow meter 2. When the control means 6 receives the meter reading data request signal, the control means 6 activates the storage means 3 and the transmission means 5. Then, the oscillation signal of the VCO 32 is frequency-modulated by the integrated data stored in the storage means 3, the frequency-modulated signal is amplified by the transmission means 5, and is radiated as a radio wave from the antenna 8 into space. The reception level detection means 43 detects the magnitude of the reception signal input from the antenna 8 and controls the reception level control means 44 so that it decreases when the reception level adjustment means 33 receives a signal with a large amplification degree. To do. The reception level control means 44 is provided with a starting terminal A. When a signal is input to the activation terminal A, the reception level control means 44 takes in the signal from the reception level detection means 43 and outputs a control signal corresponding to the taken-in signal from the reception level detection means 43 to the reception level adjustment means 33. . After that, the control signal is continuously output to the reception level adjusting means 33 regardless of the signal from the reception level detecting means 43 until the activation terminal A is input again. That is, the reception level adjusting means 3
Keep the amplification of 3 constant. The input to the starting terminal A is performed when the flow rate measuring device is attached to the gas pipe.

The frequency of the radio wave radiated from the antenna 8 is the same as the frequency of the radio wave radiated from the antenna 23. The radio wave frequency-modulated by the integrated data is received by the antenna 23 and guided to the reception level adjusting means 46. The reception level adjusting means 46 amplifies or attenuates the reception signal in the 400 MHz band. Now, through the antenna 23, S = cos {ω + p (t) * Δω} * tp (t): 1 or −1 code string ω: carrier angular frequency Δω: FSK signal represented by angular frequency deviation S is mixing means 48, 49
To enter. The VCO 45 generates a signal Q represented by Q = COS {ω + x} * tx: oscillation angular frequency error from the carrier angular frequency ω. 90 ° phase shifter 4
At 7, the signal Q from the VCO 45 is phase-shifted by 90 ° and Q ′ = SIN {ω + x} t. In the mixing means 48, VC
The signal Q from O45 and the FSK signal S are multiplied. In the mixing means 49, the signal Q ′ from the 90 ° phase shifter 47 and the FSK signal are multiplied. Then, high-frequency components other than the desired signal are removed by the low-pass filters 50 and 51, and the desired signal is amplified by the low-frequency amplification means 52 and 53. Therefore, the following signals are output to the terminals d and e.

Terminal d: S * Q = COS {p (t) * Δω−x} * t Terminal e: S * Q ′ = SIN {p (t) * Δω−x} * t Frequency correction means 55 Then, when an additional signal transmitted prior to the code string having information is received, the above-mentioned angular frequency error x
A signal for controlling the VCO 45 is output in the direction of zero. The following description will be given assuming x = 0. The relationship between the code sequence p (t) and the signal waveforms of the terminals d, e, and f is shown in FIG. 3 and will be described with reference to FIG. As apparent from FIG. 3, when the code string p (t) is -1, the phase of the signal at the terminal e is advanced by 90 ° compared to the signal at the terminal d. On the other hand, when the code string p (t) is 1, the terminal d
The phase of the signal at the terminal e is delayed by 90.degree.
Therefore, by detecting the phase difference between the signal at the terminal d and the signal at the terminal e in the phase difference detecting means 54, the original code string p
(t) can be reproduced and the original code string p (t) can be output from the terminal f. The code string p (t) output from the terminal f
Is integrated data. When the control means 21 receives the integrated data, it activates the transmitting means 20 to send a response signal to the gas flow meter indicating that the integrated data has been received via the antenna 23, and at the same time, the interface 18
The T-NCU 17 is activated via the and the integrated data is sent to the telephone line 16. The reception level detecting means 56 detects the magnitude of the reception signal input from the antenna 23,
Reception level adjusting means 4 via reception level control means 57
When a signal having a large amplification degree of 6 is received, it is controlled to be small. The reception level control means 57 has a start terminal B.
Is provided. When a signal is input to the activation terminal B, the reception level control means 57 takes in the signal from the reception level detection means 56 and outputs a control signal according to the taken-in signal from the reception level detection means 56 to the reception level adjustment means 46. . After that, the control signal is continuously output to the reception level adjusting means 46 regardless of the signal from the reception level detecting means 56 until the activation terminal B is input again. That is, the amplification level of the reception level adjusting means 46 is kept constant. The input to the starting terminal B is performed when the flow rate measuring device is attached to the gas pipe.

Next, an example of the structure of the frequency correction means 42 and 55 is shown in FIG. 4, and its operation will be described. In FIG. 4, reference numeral 58 is frequency analysis means, 59 is control means, and 60 is analog / digital conversion means. Frequency analysis means 58
Then, the signal at the terminal a is subjected to frequency analysis by the fast Fourier transform method. Consider a case where an unmodulated carrier signal is transmitted from the transmitting side prior to the bit synchronization signal of the transmitted FSK signal. At the terminal a, as described above, a signal of the terminal a: S * Q = COS {p (t) * Δω−x} * t is generated. And for an unmodulated carrier signal,
Δω = 0. Therefore, as a result of the frequency analysis by the frequency analysis means 58, the frequency x / 2π is detected. Then, in the control means 59, the VCO 32 or 4 is moved in the direction in which the frequency of the VCO 32 or 45 is slightly increased.
Control 5 If the frequency analysis result of the frequency analysis means 58 shows that the frequency is higher than the last time, the VCO
The oscillation frequency of 32 or 45 is controlled to be lowered by x / 2π. On the contrary, when the frequency becomes lower than the last time, the oscillation frequency of the oscillation means 6 is controlled to be increased by x / 2π. The analog / digital conversion means 60 converts the control signal from the control means 59 into an analog quantity and applies it to the VCO 32 or 45. By the above operation, the frequency error x / 2π can be corrected.

Another embodiment of the configuration of the frequency correction means 42 and 55 will be described with reference to FIG. Reference numeral 42 is frequency correction means, which is composed of 61 DC detection means, 62 sweep signal generation means, 63 voltage holding means, and 64 changeover switch. Consider a case where an unmodulated carrier signal is transmitted from the transmitting side prior to the bit synchronization signal of the transmitted FSK signal. First, the changeover switch 64 is adapted so that the signal from the sweep signal generating means 62 is added to the VCO 32. The sweep signal generating means 62 outputs a signal for sweeping the oscillation frequency of the VCO 32 over a certain frequency width. Then, the frequency of the signal generated at the terminal a changes according to the sweep. The DC detecting means 61 detects when the frequency of the signal generated at the terminal a becomes zero. When zero is detected, the voltage holding means 63 is activated and the changeover switch 64 is switched so that the signal of the voltage holding means 63 is applied to the VCO 32. Further, the operation of the sweep signal generating means 62 is stopped. The voltage holding means 63 holds the signal level from the sweep signal generating means 62 by the signal from the DC detecting means 61. With the above operation, the oscillation frequency of the VCO 32 matches the carrier frequency of the FSK signal input to the antenna.

[0016]

As described above, according to the flow rate measuring apparatus of the present invention, the integrated data from the flow meter is multiplied by the same frequency as the carrier frequency on which the integrated data is put, and converted into a low frequency signal, and then the integrated data is converted. Since it is configured to demodulate, the ratio of the high frequency signal part can be reduced, and the low frequency signal part can be made into a monolithic IC, so that the flow rate can be easily measured even without knowledge of the high frequency circuit. The device can be assembled.

Further, a VCO which is an oscillating means for transmission
In addition, since the VCO that is the oscillating means for reception can be shared and the transmission and reception can be performed by one VCO, it is easy to maintain the frequency stability, and the reliability of the integrated data in the automatic meter reading can be improved. it can.

FS to be received by the frequency correction means
Since the correction can be performed so that the carrier frequency of the K signal and the oscillation frequency of the oscillating means match, the transmitted integrated data can be reproduced even with an FSK signal having a large angular frequency deviation.

Further, since the flow rate measuring device can be adjusted by the reception level adjusting means so that the reception signal level becomes optimum when it is installed in each home, the reliability in receiving the integrated data can be further improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a relay device section on a flow rate measuring side which constitutes a flow rate measuring device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a repeater unit on the T-NCU side that constitutes a flow rate measuring device according to an embodiment of the present invention.

FIG. 3 is an output diagram of each output terminal in one embodiment of the present invention.

FIG. 4 is a block diagram of frequency correction means in an embodiment of the present invention.

FIG. 5 is a block diagram of frequency correction means in another embodiment of the present invention.

FIG. 6 is a block diagram of a conventional flow rate measuring device.

[Explanation of symbols]

1 gas pipe 2 Flow meter 3 storage means 32 VCO 33 Reception level adjusting means 41 Phase difference detection means 42 Frequency correction means 43 Reception level detection means 44 Reception level control means

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-2-32648 (JP, A) JP-A-2-149155 (JP, A) JP-A-4-294499 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G08C 15/00 H04M 11/00 301

Claims (5)

(57) [Claims] 1. Storage means for measuring and storing measurement data of a flowmeter, transmission means for transmitting measurement data from the storage means on a carrier wave signal, and requesting transmission of measurement data from the storage means. Reception means for receiving a request signal or a response signal to the measurement data, reception level detection means for detecting the level of the reception signal received by the reception means, and reception level adjustment for adjusting the reception signal level received by the reception means Means, and a reception level control means for controlling the reception level by outputting one of a plurality of predetermined output signals corresponding to the reception level from the reception level detecting means to the reception level adjusting means, An activating terminal for activating the reception level control means, wherein the reception means oscillates at a frequency close to a carrier signal frequency to be received. A first mixing means for taking out a difference signal between the signal from the oscillating means and the received signal, and a second mixing means for taking out a difference signal between the signal obtained by phase-shifting the signal from the oscillating means and the received signal, Phase difference detection means for detecting a phase difference between the signal from the first mixing means and the signal from the second mixing means,
A flow rate measuring device comprising a frequency correction means for detecting a difference between a carrier signal frequency to be received and a signal frequency from the oscillating means and controlling the oscillation frequency of the oscillating means in a direction of eliminating the frequency difference. 2. Data collection means for collecting measurement data of a flow meter, and transmission means for transmitting a data collection request signal from the data collection means or a response signal to the measurement data from the flow meter on a carrier wave. Receiving means for receiving the measurement data from the flow meter, receiving level detecting means for detecting the level of the receiving signal received by the receiving means, and receiving level adjusting means for adjusting the receiving signal level received by the receiving means. Receiving level control means for controlling the receiving level by outputting one of a plurality of predetermined output signals corresponding to the receiving level from the receiving level detecting means to the receiving level adjusting means, and the receiving level An activating means for activating the control means, the receiving means oscillating means for oscillating at a frequency close to a carrier signal frequency to be received; A first mixing means for extracting a difference signal between the signal from the oscillating means and the received signal; a second mixing means for extracting a difference signal between the signal obtained by phase-shifting the signal from the oscillating means and the received signal; Phase difference detecting means for detecting a phase difference between a signal from one mixing means and a signal from the second mixing means, and a difference between a carrier signal frequency to be received and a signal frequency from the oscillating means. And a flow rate measuring device configured with frequency correction means for controlling the oscillation frequency of the oscillation means in the direction of eliminating the frequency difference. 3. The flow rate measuring device according to claim 2, wherein the data collecting means has a network control means connected to a telephone line. 4. A frequency correction means, a frequency analysis means for frequency-analyzing a signal from the first or second mixing means, and a control means for generating an output according to a frequency component detected by the frequency analysis means, The flow rate measuring device according to claim 1 or 2, further comprising: a digital / analog conversion means for supplying a DC voltage for controlling an oscillation frequency of the oscillation means by a signal from the control means. 5. The frequency correction means includes sweep signal generating means for sweeping the oscillation frequency of the oscillating means, direct current detecting means for detecting a direct current signal from the signal from the first or second mixing means, and sweeping. A voltage holding means for holding the sweep signal from the signal generating means by the signal from the DC detecting means, and a signal for controlling the oscillating means by the signal from the DC detecting means and the voltage from the sweep signal generating means. The flow rate measuring device according to claim 1 or 2, comprising a switching means for switching to a signal from the means.