Level Measurement with Radar and UltrasonicNorCal Tech 2005 Technical Conference

Level Measurement with Radar and Ultrasonic

Level Measurement with Radar and UltrasonicTechnologies

Through AirRadar

Guided Wave

Radar

Ultrasonic

Level Measurement with Radar and UltrasonicHow 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%100%

0%0%

Level Measurement with Radar and Ultrasonic

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?

Process conditions that affect specification of transmitters

Level Measurement with Radar and Ultrasonic

Through Air Radar

Level Measurement with Radar and UltrasonicRadar 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.

Level Measurement with Radar and UltrasonicFunction 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

Level Measurement with Radar and Ultrasonic

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 – Why use it?

Level Measurement with Radar and UltrasonicRadar Technology - Choice of frequency

Radar wavelength = Speed of light / frequency = c / f

Frequency 6.3 GHz

wavelength = 47.5 mm

Frequency 26 GHz

wavelength = 11.5 mm

High frequency:

shorter wavelength

narrower beam angle

more focused signal

ability to measure smaller vessels

with more flexible mounting

47.5mm47.5mm

11.5mm11.5mm

Low frequency:

longer wavelength

wider beam angle

less focused signal

ability to measure in vessels with

difficult application variables

Level Measurement with Radar and Ultrasonic

5 GHz 10 GHzFrequency

Comparison of horn diameters that produce the same beam angle

20 GHz15 GHz 25 GHz

Focusing at 6.3 GHz:

Horn size Beam angle

3“ 38°

4“ 33°

66" 21°21°

10“ 15°

Focusing at 26 GHz:

Horn size Beam angle

1.51.5" 22°22°

2“ 18°

3“ 10°

4“ 8°

Radar Technology – Focusing of Frequency

30 GHz

6.3 GHz6.3 GHz 26 GHz26 GHz

(A shorter wavelength means a smaller antenna for the same beam angle)

Level Measurement with Radar and UltrasonicMajor Factors in Specifying a Radar - Frequency

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)

Level Measurement with Radar and UltrasonicRadar Technology – Choosing a frequency

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

No single frequency is ideally suited for every radar level application.

Level Measurement with Radar and Ultrasonic

Guided Wave

Radar

(TDR)

Level Measurement with Radar and UltrasonicGuided 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

Level Measurement with Radar and UltrasonicPrinciple 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.

Level Measurement with Radar and UltrasonicApplication Examples

• Installation into the vessel

• Installation in bridles without worry of build-up or interference from side leg connections

• Ideal for replacement of displacers

Level Measurement with Radar and UltrasonicApplication Examples

• Interface Measurement• Oil/Water• Solvent/Water

Level Measurement with Radar and UltrasonicGuided 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• Top 6 inches• Bottom 0 inches

Concentric Tube• Top: 1.6 inches• Bottom: 0.8 inches

Level Measurement with Radar and Ultrasonic

Ultrasonic

Level Measurement with Radar and UltrasonicUltrasonic Level Measurement

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)

Level Measurement with Radar and UltrasonicUltrasonic 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

Level Measurement with Radar and UltrasonicUltrasonic 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

Level Measurement with Radar and UltrasonicUltrasonic 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

Level Measurement with Radar and UltrasonicQuestions?

Questions?