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1.
INTRODUCTION
Application
The MicroTREK 2-wire level gauge uses the Time Domain Reflectometry (TDR) measuring principle and two-wire technology for level measurement.
It is designed for measuring distance, level and volume of liquids, pastes, slurries and powder mediums.
The device is applicable in tank, silo, rigid pipe, reaction-vessel and level reference vessel.
The device is HART
®
capable, it can be programmed using a HART
®
Handheld Communicator (HHC), a MultiCONT universal process controller and EView2 software
supplied as standard with the gauge.
Operating principle
The MicroTREK 2-wire guided microwave level transmitter uses the TDR (Time Domain Reflectometry) principle. The instrument sends low power nanosecond wide
pulses along an electrically conductive rod, cable or coaxial probe with a known propagation speed (the speed of light). As the pulse reaches the surface of the medium
or phase of two liquids (altered dielectric constant
r
), a part of it is reflected back to the electronic module. The efficiency of the reflected signal depends on the
dielectric constant
r
difference of the mediums or layers. (From the plain surface of air-water phase the reflected signal's strength will be approx. 80% of the emitted
signal). The reflected pulse is detected as an electrical voltage signal and processed by the electronics. Level distance is directly proportional to the flight time of the
pulse. The measured level data is converted into 4 – 20 mA current and HART signals and is displayed on the LCD display. From the level data further measuring
values can be calculated such as volume and mass. The TDR technology is unaffected by the other properties of the medium as well as of the space above it.