The best choice of the hottest ultrasonic gas mete

The best choice of ultrasonic gas meter

with the continuous improvement of living standards, people are more and more environmental friendly, and the seriously polluted conventional energy is gradually abandoned by people. The state also introduced the gas pipeline policy and corresponding measures in the 1960s and 1970s. With the construction and popularization of gas transmission pipelines, gas meters have sprung up, from mechanical to electronic, from mode to ultrasonic, and new concepts and technologies continue to emerge, reflecting people's pursuit of high quality

at present, there are two mainstream gas meters in the market, one is the traditional mechanical membrane gas meter, the other is the electronic membrane gas meter, and the ultrasonic gas meter is emerging in the gas meter market with a strong momentum

principle and advantages and disadvantages of mechanical membrane gas meter

mechanical membrane gas meter is realized by mechanical roller. The mechanical roller adds one according to the gas volume used. For each unit used, the roller technology adds one, and finally realizes the gas volume measurement record. When the flowing gas passes through the gas meter, it is blocked by pipeline friction and mechanism. Considering the requirements of product characteristics, utilization and durability, the internal gas will produce a pressure difference at both ends of the inlet and outlet of the gas meter. Through this pressure difference, the diaphragm of the membrane gas meter will move in the measuring room, and the gas distribution mechanism will be driven to coordinate the gas distribution, so that the movement of the diaphragm can be continuously reciprocating, The membrane gas meter converts the linear reciprocating motion into circular motion through the internal mechanical structure, and then drives the mechanical roller counter to rotate through the circular motion; Each time the diaphragm reciprocates, a certain amount of gas will be discharged, and finally the roller will rotate a technical unit to realize the metering and display effect of roller rotation

Figure 1: mechanical membrane gas meter (roller)

the advantages of mechanical membrane gas meter are mature technology, reliable measurement and stable quality, but its development is hindered by its complex structure, large volume and large manual meter reading cost

principle and advantages and disadvantages of electronic membrane gas meter

electronic membrane gas meter is improved on the basis of traditional mechanical type, adding electronic metering mode, display function, prepayment and remote meter reading function, and realizing semi electronic. We know that the national standard for high temperature tensile test stipulates that the round specimen is ribbed

Figure 2: the core part of the electronic membrane gas meter is to increase the electronic metering mode. Usually, a magnet is installed on the mechanical roller at the highest accuracy position, and two dry reeds are installed above and below the roller. When the magnet does not reach the dry reed position, the two dry reeds are disconnected; When the magnet turns to one of the clarinet positions, the clarinet pulls in

Figure 3: principle of electronic membrane gas meter

if configured according to the above circuit diagram, the circuit waveforms S0 and S1 in the right part of Figure 3 will be output, and the single chip microcomputer will judge these two groups of waveforms to get the working state of the gas meter. When S0 and S1 have a low pulse successively, it is judged as effective pulse measurement, and then the pre stored fuel gas purchase can be reduced; When S1 (or S0) does not output pulses between the two pulses output by S0 (or S1), it can be judged that S1 (or) S0 of the gas meter has a fault, and some fault handling should be done, such as alarm, valve closing and other operations

the electronic membrane gas meter has little technical improvement, and the measurement reliability is guaranteed. The new electronic measurement method realizes semi electronization, and effectively solves the problem of manual meter reading. But its complex structure and huge volume still restrict its development

ultrasonic gas meter

under the current market situation, a new mode of higher technology, optimizing structure and solving cost problems came into being. Ultrasonic gas meter is pushed into the market under this situation

although ultrasonic gas meters are just emerging, their advantages are obvious compared with the current mainstream model. Ultrasonic gas meter has incomparable advantages in mechanical noise, accuracy, range, repeatability, service life and maintenance compared with previous mechanical meters due to its full electronic mechanism characteristics. Ultrasonic gas meters have begun to enter the civil market in Europe and Japan. For the Chinese gas meter market with about tens of millions of capacity, the considerable prospect of ultrasonic gas meters will certainly bring a new development opportunity to potential Chinese manufacturers

Figure 4: ultrasonic gas meter

principle of ultrasonic gas meter:

Figure 5: working principle of ultrasonic gas meter

first send ultrasonic wave from upstream to downstream, and measure the flight time T1 of ultrasonic wave

secondly, send ultrasonic wave from downstream to upstream, and measure the flight time of ultrasonic wave t2

in view of the difference between these two flight times, the rate of gas can be obtained through the following formula. With the velocity and the volume of the pipe section, the flow can be calculated

advantages of ultrasonic gas meter:

because it is fully electronic, there is no mechanical part, and it is not affected by mechanical wear and failure, the reliability and accuracy of the product are greatly improved. Small size, light weight, good repeatability, small pressure loss, not easy to aging, long service life; Intelligent, all electronic structure, which can be extended to prepaid meter or wireless meter reading function

acam GP2 scheme

for the market of ultrasonic gas meters, Shiqiang Telecom brings ACAM GP2 scheme to assist you in the design of ultrasonic gas meters

the core of this scheme is the time digital conversion chip TDC-GP2 of ACAM company. TDC-GP2 has a high-precision time measurement function, with a resolution of 65ps, which provides a basic measurement guarantee for the application of time difference flowmeter; The pulse generator of TDC-GP2 can directly drive the ultrasonic transducer in the flow measurement of small diameter without adding another driving chip; The low power consumption characteristic measured by TDC-GP2 greatly reduces the overall power consumption of the flowmeter and provides an excellent solution for battery powered equipment

compared with the ultrasonic flowmeter scheme using discrete components or FPGA, the ultrasonic flowmeter scheme using ACAM TDC-GP2 greatly simplifies the hardware circuit design. It can complete the design of control and time measurement circuits only by matching MCU and simple comparator and analog switching elements. This scheme simplifies the circuit design, greatly reduces the PCB area of the equipment, and makes the production and maintenance of the equipment more convenient and easy

tdc-gp2 also has two-way temperature measurement function, which can be directly connected to PT1000 or PT500 thermistor for temperature measurement, which provides an integrated solution for the application of heat meters

gp2 advantages:

1, high-precision analysis. The typical accuracy of a single time interval measurement of TDC-GP2 is 65ps, that is to say, the internal time of passing through a logic gate is determined to be about 65ps. TDC-GP2 has very good statistical characteristics. Through multiple average measurements, the typical accuracy of time measurement can be reduced to about 10ps. Such data can also obtain very good accuracy when measuring a small flow (such as 1.6m3/h)

2. Low power analysis. GP2 will measure in the form of pulses. Especially in ultrasonic measurement, the core measurement unit of TDC is not working all the time. It only measures the rising edge of the start signal to the rising edge of the next reference clock and the rising edge of the stop signal to the rising edge of the next reference clock, and the intermediate time is completed by calculating the number of cycles of the reference clock. Such a measurement principle reduces the power consumption of the measurement time to a very low level. The current consumption of the whole system is μ Within the scope of A. If the low-power microprocessors are installed correctly; If the device (such as the c8051f92x/93x series of silabs), the average power of the whole device adopts the discontinuous fabric material stacking method, which will cause the waste of raw materials and reduce the consumption of flow μ A。 (end)