E+H Radar Measurement Micropilot FMR51 Series Liquid Level Instrument Radar Measurement Time-of-Flight Micropilot FMR51

What is Radar Time-of-Flight Level Measurement

• It’s a non-contact method to measure level (height) of liquids, pastes, slurries etc., inside a vessel or tank.
• The instrument emits short microwave pulses (radar impulses) downward from a reference point (usually the process connection). These pulses travel through air or vapor, reflect off the surface of the medium, and return to the antenna.
• The key measurement is the time of flight (ToF), i.e. how long the pulse takes to go from the device to the surface and back. Since electromagnetic waves travel at the speed of light (modified by the medium), the distance can be calculated as:

D=c⋅t2D = frac{c cdot t}{2}D=2c⋅t​

where
DDD = distance from reference to the surface
ttt = round-trip time
ccc = speed of light (in the medium, usually close to in air)

• From that distance, knowing the “empty” height (or reference point), the actual level (how full) of the tank is derived.
• Because the measurement is non-contact, there is no immersion of the instrument into corrosive or difficult media; fewer issues with buildup, corrosion, etc. Also less maintenance and easier safety/hygiene compliance.

Micropilot FMR51 — Overview & Key Features

The Micropilot FMR51 is a radar ToF level transmitter from Endress+Hauser, optimized for aggressive liquids and hygiene-sensitive applications.

Here are its important specifications, strengths, and special features:

Strengths & Advantages

• Non-contact: No sensor submerged; less affected by buildup, corrosion, fouling. Better hygiene, especially important in food / pharma / biotech.
• Wide range and robust under harsh conditions: High temperature, pressure, aggressive chemicals tolerated.
• High accuracy even over long distances.
• Good for changing media: Changes in dielectric constant, presence of vapors/gas above the liquid, changing surface conditions (ripple, foam) are better handled than many other sensors.
• Diagnostics & maintenance features: Helps in predictive maintenance; less downtime.
• Compliant with regulatory / safety / hygienic standards: Important for regulated industries.

Limitations & Things to Consider

• Cost: More expensive than simple contact or ultrasonic level sensors.
• Installation constraints: Antenna needs to have a clear “field of view”; avoid obstructions (agitators, pipes, nozzles); mounting height and position matters.
• Gas/vapor layers: Large layers of gas or vapor (especially under pressure) can slow propagation and introduce error unless compensated. FMR51 has correction or compensation features.
• Surface conditions: Very turbulent, foamy, or very low reflectivity surfaces make echo detection harder.
• Dielectric constants: If medium has very low dielectric constant (εr), reflections are weaker; need good antenna design and signal processing.
• Maintenance of “flush mounting / PTFE sealing”: Over time seals/antennas may need inspection, cleaning to ensure proper functioning.

Typical Applications

• Level measurement in chemical plants handling corrosive liquids.
• Food & beverage / biotech plants where hygiene is critical (dairy, breweries, pharmaceutical tanks).
• Storage tanks for aggressive chemicals.
• Slurries, pastes where contact sensors would degrade.
• Large tanks with long range requirements.