NorCal Tech 2005 Technical Conference Level Measurement with Radar and Ultrasonic

Technologies Through Air Radar Guided Wave Radar Ultrasonic

How it works The time it takes for the instrument’s signal to leave the antenna, travel to the product, and return to the antenna is calculated into distance. The instrument is spanned according to the distance the 100% and 0% points within the vessel are from its reference point. The measured distance can then be converted into the end user’s desired engineering unit and viewed on the head of the instrument or remote display. 100% 0%

Process conditions that affect specification of transmitters How do process conditions affect the reliability and accuracy of process level transmitters ? density (specific gravity)? dielectric constant? conductivity? temperature? pressure? vacuum? agitation? vapors and condensation? dust and build up? internal structures?

Through Air Radar

Radar Technology – How it works Radar is a time of flight measurement. Microwave energy is transmitted by the radar. The microwave energy is reflected off the product surface The radar sensor receives the microwave energy. The time from transmitting to receiving the microwave energy is measured. The time is converted to a distance measurement and then eventually a level.

reduction of the antenna ringing optimization of the beam Function of an antenna Signal focusing reduction of the antenna ringing optimization of the beam Signal amplification focusing of the emitted signal amplification of the receipt signal Signal orientation point at the product surface minimization of false echo reflections

Radar Technology – Why use it? Radar level measurement Top mounted Solids and liquids applications Non-contact RADAR is virtually unaffected by the following process conditions: Temperature Pressure and Vacuum Conductivity Dielectric Constant (dK) Specific Gravity Vapor, Steam, Dust or Air Movement Build up (depends on radar design)

Radar Technology - Choice of frequency Radar wavelength = Speed of light / frequency l = c / f 47.5mm Frequency 6.3 GHz wavelength l = 47.5 mm 11.5mm Frequency 26 GHz wavelength l = 11.5 mm High frequency: shorter wavelength narrower beam angle more focused signal ability to measure smaller vessels with more flexible mounting Low frequency: longer wavelength wider beam angle less focused signal ability to measure in vessels with difficult application variables

Radar Technology – Focusing of Frequency Comparison of horn diameters that produce the same beam angle (A shorter wavelength means a smaller antenna for the same beam angle) Focusing at 6.3 GHz: Horn size Beam angle 3“ 38° 4“ 33° 6" 21° 10“ 15° Focusing at 26 GHz: Horn size Beam angle 1.5" 22° 2“ 18° 3“ 10° 4“ 8° 6.3 GHz 26 GHz 5 GHz 10 GHz 15 GHz 20 GHz 25 GHz 30 GHz Frequency

Major Factors in Specifying a Radar - Frequency Choosing a frequency depends on: Mounting options Customer’s 100% point Vessel dimensions – proximity of connection to sidewall The presence of foam Agitated product surfaces Vapor composition Vessel internal structures Dielectric constant (dK)

Radar Technology – Choosing a frequency No single frequency is ideally suited for every radar level application. Low Frequency – 6.3 GHz – C-band Better Performance with: Heavy Agitation Severe Build-up Foam Steam Dust Mist Dish bottom vessels Typical accuracy: +/- 10mm High Frequency – 26 GHz – K-band Small Process Connections Very little “near zone” Recessed in nozzles Less susceptible to false echoes Reduced antenna size Perfect for small vessels Able to measure lower dK products without using a stilling well. Typical accuracy +/- 3-5mm

Guided Wave Radar (TDR)

Guided Wave Radar Measurement Guided Wave Radar level measurement Time of Flight Top mounted Solids and liquids applications Contact Measurement GUIDED WAVE RADAR is virtually unaffected by the following process conditions: Temperature Pressure and Vacuum Conductivity Dielectric Constant (dK) Specific Gravity Vapor, Steam, or Dust Air Movement Build up (depends on type of build up) Foam

Principle of Operation A microwave pulse (2 GHz) is guided along a cable or rod in a 20” diameter or inside a coaxial system. The pulse is then reflected from the solid or liquid, back to the head of the unit. The travel time of the pulse is measured and then converted to distance.

Installation into the vessel Application Examples Installation into the vessel Installation in bridles without worry of build-up or interference from side leg connections Ideal for replacement of displacers

Interface Measurement Oil/Water Solvent/Water Application Examples Interface Measurement Oil/Water Solvent/Water

Guided Wave Radar – Accuracy & Dead Zones Typical Accuracies Cable +/- 5 mm Rod +/- 5 mm Concentric Tube +/- 3 mm Typical Dead Zones or Blocking Distances Cable Top 6 inches Bottom 9.8 inches includes weight – 6” Rod Bottom 0 inches Concentric Tube Top: 1.6 inches Bottom: 0.8 inches

Ultrasonic

Ultrasonic Level Measurement Time of Flight Top mounted Solids and liquids applications Non-contact ULTRASONIC is virtually unaffected by the following process conditions: Change is product density (spg) Change in dielectric constant (dk)

Ultrasonic Level Measurement – How it works Time of Flight Technology Short ultrasonic impulses emitted from transducer Bursts are created from electrical energy applied to piezeo electric crystal inside the transducer The transducer creates sound waves (mechanical energy) With longer measuring ranges a lower frequency and higher amplitude are needed to produce sound waves that can travel farther The longer the measuring range the larger the transducer must be

Ultrasonic Level Technology – Advantages Can be mounted in plastic stilling wells Narrow beam angles minimize effect of obstructions Swivel flange available for applications with angles of repose Familiar technology throughout the industry, therefore, often a trusted technology throughout the industry Cost-effective

Ultrasonic Level Technology – When to use it Vessels with products whose characteristics remain constant Water Bulk solids Storage Vessels Where repeatability is not critical Typical Accuracy +/- 5-10 mm

Questions? Questions?