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The measurement of level of highly contaminated waters and aggressive liquids belongs to the category of diffcult measurements. These operational conditions are very demanding particularly to the measuring device quality, lifetime and measurement reproducibility. The most common measurement devices are the ultrasonic or tensometric instruments. However, their use can be limited in difficult environments. The stainless steel diaphragm does not last a long time in aggressive liquids and it clogs in biologically contaminated waters with different deposits, which influence the diaphragm quality and consequently the measurement precision. Ultrasonic devices are relatively expensive and they are not appropriate for all applications, e.g. in the case of intermittent existence of a thick floating foam layer they can not measure the level. To avoid the above mentioned problems we have developed an instrument based on indirect measurement method. The instrument has a relatively low price and allows to achieve high precision, reliability and especially the high resistance to aggressive liquids regardless of temperature. It is the so called bubble method. A miniature electromagnetic pump emits specific quantity of air into a closed system and displaces the liquid from the immersed part of the tube. At the moment when the displacement begins, starts the bubbling. The pressure in the closed pneumatic system equilibrates on the value equal of liquid hydrostatic pressure and the height of the immersed part of tube. The air emitted by the pump is set so that the bubbling is minimal and system pressure changes are negligible. The electromagnetic pump is time controlled and it works in impulse mode. The energy consumption of this instrument is decreased while its lifetime is increased. The pressure is measured with a pressure probe having a 4 to 20 mA or 0 to 20 mA output, the system power supply is 24 V/80 mA. The material of the immersed tube is selected according to the medium to be measured (plastic, glass). The bubbling has an important role in cleaning the tube orifice and removes deposits and sediments.The device application possibilities are very wide. One possible application is the flow measurement. We supply the optional measuring control systems for the technological process evaluation and control. We also deliver different types of measuring channels, which in association with level measurement measure the flow in different industrial applications, especially in waste water treatment and sludge measurement applications. We produce the MVOFIX measuring device in two versions. The basic one has a cylindrical shape and a standard 4 to 20 mA current output. The enhanced version is supplemented with a 3½ - cell LCD display showing the measured values. In this case the measurement device is installed in a plastic box manufactured by SAREL company. |
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Technical specifications: | |
| Maximálny range (scaleable) | 0 - 10m |
| Measurement precision | ± 0,25%, ± 0,5% |
| Supply voltage | 35V/80mA |
| Output signal | 4 - 20mA, 0 -20 mA, 0 - 1V, 0 - 5V |
| Temperature of the measured liqid | irrelevant |
| Operational temperature | -25 - 70°C |
| Connection | two-wire, three-wire |
| Dimensions | diameter = 50mm, length = 250mm |