1. NorCal Tech 2005 Technical Conference
Level Measurement with Radar and Ultrasonic

2. Technologies
Through Air
Radar
Guided Wave
Radar
Ultrasonic

3. 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%

4. 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?

5. Through Air Radar

6. 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.

7. 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

8. 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)

9. 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

10. 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

11. 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)

12. 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

13. Guided Wave
Radar
(TDR)

14. 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

15. 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.

16. 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

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

18. 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

19. Ultrasonic

20. 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)

21. 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

22. 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

23. 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 +/ mm

24. Questions?
Questions?