Electromagnetic Water Meters Capable of Measuring Bubbling Fluid
In Japan, normally, tap water is supplied during 24 hours, and is always under water supply pressure; meanwhile, in emerging countries or desert regions, it is often the case that water is supplied only for several hours a day, and households or communities are sometimes provided with tanks to store water for use during water supply hours. Therefore, during hours when water is not supplied, supply pressure is not applied and water pipes become empty, and afterwards, when water supply is resumed and water passes through the water pipes again, water takes in air accumulating in the water pipes. As a result, bubbling water runs through water meters. This is why water operators there have the problem that they cannot correctly charge water rates. We are researching measuring technology for bubbling fluid, in order to provide water operators who need to measure the flow of such bubbling water with water meters that only and correctly measure the flow of passing water.
The measurement of bubbling fluid is becoming a new function required by not only water operators, but also industries, such as petrochemical plants and food processing plants, that need to accurately measure the accepted, prepared, supplied, blended or added amount of bubbling liquid. Also, ultrasonic flowmeters, competitor devices, cannot measure the flow of bubbling liquid because of their measuring principles, and therefore, the development of electromagnetic flowmeters with a function to measure bubbling fluid can result in a new differentiation technology.
How to measure bubbling fluid
The measuring error of electromagnetic water meters and impeller water meters tends to increase in a positive direction as the bubbling rate rises. Ultrasonic water meters are not suitable for measuring the flow of bubbling liquid because of their measuring principles. And impeller water meters have noticeable measurement error. Among these types of meters, electromagnetic water meters are superior in resistance to bubbling.
If the measuring error is determined by the bubbling rate, calculating the bubbling rate allows error compensation, making it possible to develop water meters that only and accurately measure the flow of passing water.
■ Calculation of bubbling rate by means of process tomography method (patent pending)
We conducted joint research with Chiba University for two years from FY 2016 to 2017, and acquired calculation technology for bubbling rates in measured fluid by means of a process tomography method that uses multipoint electrodes.
The process tomography method is a measuring technology to visualize the multiphase flow of solid, liquid, or gas in the flow path in real time by means of an original algorithm. In this method, multiple electrodes are placed around the flow path, and the impedance between each electrode is measured at high speed.
In the research, the process tomography method was applied to perform the following series of operations in the order of milliseconds by means of a high-speed switching circuit and original algorithm:
- ① Apply alternating voltage to one electrode to measure the impedance between each electrode
- ② Change the electrode to which voltage is applied
- ③ Carry out measurement on all combinations of electrodes
If there are bubbles between electrodes, the impedance between the electrodes becomes high; therefore, the measurement for the full water capacity（ⅠΗ）and the measurement for a bubbling state（Ｉ）are computed to calculate the bubbling rate.
(We and Chiba University have jointly applied for a patent for the system, circuit configuration, and measuring algorithm.)
Voice of developers
Our research collaborator from the university was Korean, so we had to communicate in our poor English or body language with difficulty to have technical discussions or to introduce technology.
Also, we used the university’s common research facilities to carry out experiments, so we had a limited amount of time to make a plan and to generate a result and this made us feel pressure. We, however, feel the joy of working on development with a dream of introducing new technologies to Aichi to develop new products.