סדרת משדר מפלס מבוססים רדאר (TDR)
Time Domain Reflectometry
|למדידת מפלס נוזלים ומוצקים |
אינו תלוי במשקל סגולי, טמפרטורה, לחץ
|אורך מקסימלי: עד 20 מטר|
|תחום טמפרטורה: C ° -150...250 |
|תחום לחץ: bar -1...40 |
|יציאה: 4-20mA, מגעים PNP|
|אופציה: תקן מוגן פיצוץ אירופאי.ATEX ||
The modularly constructed NGM of KOBOLD works on the principle of Time Domain Reflectometry (TDR, also known as guided Microwave or guided Radar) and offers an excellent alternative to conventional level measurements. The NGM enables precise and reliable continuous level measurement and point level detection in almost all liquids. This innovative device has almost no installation restrictions - it can be mounted in small tanks, tall and narrow nozzles and it measures precisely even with difficult tank geometries or close to interfering structures.
Exact and speedy level measurement is a challenge, especially in small vessels. Small vessels can have very high filling speeds (approx. 200-400 mm/s, depending on the pump used), so that fast response times are necessary. Conventionally, capacitance level meters have been used in small tanks.
The disadvantages of capacitance level meters are their dependence on medium dielectric constants and a specific probe calibration in tanks. NGM is ideal for various types of processing and storage applications and has an exceptional performance in liquids with low dielectric constants (low reflectivity) such as oils and hydrocarbons. NGM uses TDR Technology: low-energy, high frequency electromagnetic impulses, generated by the sensor´s circuitry, are propagated along the probe which is immersed in the liquid to be measured. When these impulses hit the surface of the liquid, part of the impulse energy is reflected back up the probe to the circuitry which then calculates the fluid level from the time difference between the impulses sent and the impulses reflected. The sensor can output the analysed level as a continuous measurement reading through its analogue output, or it can convert the values into a freely adjustable switching output signal.
The existing 2-wire TDR-meters have restricted speeds, as only limited energy is available. The NGM is a 4-wire unit with sufficient power to measure evidently fast and reliable. The NGM measures up to 70 times per second, a 2- wire unit in contrast only once a second. This means, that the NGM generates many folds more measuring data each second, which can then be used for a reliable evaluation of level signal. The 2-wire meters mostly require 10 to 40 seconds to determine the level value. Fast level changes (e.g. in small vessels) may well lead to wrong level interpretation. The NGM offers a standard reaction time of 0.5s and can detect level changes of up to 1000 mm/s without any problems. The advantages of NGM in small tanks are thus unmatchable. The 4-wire design offers a highly robust measurement due to innovative signal analysis and disturbance signal suppression. A fully modular probe design enables simple installation and keeps the instrument economically priced.
Unlike older technologies, TDR offers measurement readings that are independent of the chemical or physical properties of the process media with which it is in contact.
NGM is suitable for a variety of level measurement applications including those that involve:
- Unstable process conditions - Changes in viscosity, density, or acidity do not affect accuracy.
- Agitated surfaces - Boiling surfaces, dust, foam, and vapour do not affect device performance.
TDR also works with re-circulating fluids, propeller mixers, and aeration tanks.
- High temperatures and pressures - NGM performs well in temperatures up to +250 °C and can withstand pressures up to 40 bar.
- Fine powders and sticky fluids - NGM works with vacuum tanks filled with used cooking oil as well as tanks holding paint, latex, animal fat, soybean oil, sawdust, carbon black, titanium tetrachloride, slat, and grain.
- Hazardous area ATEX cerification
Factory settings may be configured via HART® Modem.