M
Kindly provide exhaustive details on difference between Ultrasonic Level transmitter & Radar Type Level transmitter. Pl provide link if possible.
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A.C.Sankaranarayanan
Hi,
Please can you visit http://www.vega.com
We use all kind of transmitters used by this product. You can also check with "Endrass+Hausser".
bye...
Please can you visit http://www.vega.com
We use all kind of transmitters used by this product. You can also check with "Endrass+Hausser".
bye...
D
Dan
Comparing ultrasonics and radar:
Both ultrasonics and radar are top mount, non contact technologies. Ultrasonics is slightly older in commercial use than radar, but the price on radar has dropped in the last 5 years to make it much more common and competitive with ultrasonics. Ultrasonic is now about 5th
generation.
Both technologies can be 2 wire, 2 wire I.S. (intrinsically safe) or EXP (explosion proof) or 4 wire EXP. The long shot devices are 4 wire for power reasons.
All brands have models that come as 4-20mA transmitters. I think all radars are one piece, with no remote mount electronics like ultrasonics can have. Ultrasonics historically has had the ability to have multiple transducers operate from a single electronics box, radar has no such
option. The electronic boxes can have level controllers with relay or analog outputs and digital communications like Modbus. The electronic boxes also typically mount on the ground at eye level, so that operators can keep track with local indication, compared to indicators built into the transmitters themselves, on the top of the tanks, which in many cases are not easily accessible.
Radar's main limitation is found in the dielectric of the material it is shooting. Low dielectrics (good insulators, poor conductors like hydrocarbons) can be problematic for radar. Radar shoots through low dielectrics.
Ultrasonics has a substantial blanking zone directly beneath the transducer/antenna. A radar rod antenna can have an extended length
that is as deep (300mm) as an ultrasonic blanking zone.
When installing a device with a long antenna, one must have sufficient head room above the tank to angle the antenna into the tank. Some
indoor sites with low roofs and high tanks can't handle the installation of a long antenna.
Sometimes tank usage requires a tank level to approach the top of the tank. Radar doesn't operate inside an elevated stand-off, its antenna has to be below the standoff, extended there by a "shield". An ultrasonics
unit is very likely to operate in a reasonably sized stand-off (depends on ratio of diameter to height). This gives ultrasonics a better edge for close-to-the-top level applications, because radar's antenna will extend lower than an ultrasonic transducer in a standoff, even accounting for ultrasonic's
blanking zone.
Both the radar horns and the ultrasonic transducers increase in size for longer distance shots, requiring larger access ports.
Domed top tanks - some radars can't take mounting in the center of a domed top - the parabolic effect of the dome gives them problems.
Both technologies have mixed reactions to dished bottom tanks. Some can handle it, some can't, usually a try-and-see basis.
Radars handle higher pressures, both from a materials/construction perspective and from a technology standpoint. Increased pressures mean
varying ultrasonic velocity rates, with the attendant problem of shifting calibration with shifting pressure. Only radar goes on a pressurized reactor.
Temperature limits are somewhat lower on ultrasonics because of the materials used for the transducer. The horns on radar lend themselves better to high temp functionality, but the electronics still have to located
to where it is cool enough to survive. But I've put radar in hot zones where ultrasonics would have burned up in 3 minutes (had to air purge
cool the transmitter head).
Liquid measurements require the instrument to be plumb, solids measurements frequently make use of some sort of adjustable, tiltable aiming device due to solids' angles of repose.
Both technologies can be fussy about deposits on the transducer or horn. There are photographs circulating that would lead one to believe
otherwise, but I offer a word of warning to wise.
Both technologies cannot be disturbed by nearby inlet streams that intersect their beams.
Both technologies have to deal with obstructions inside tanks: agitators, ladders, eating/cooling coils, baffles ,welds, debris, access ports,
support struts, etc. Some do better than others, not by technology, but by vendor algorithm.
I have used ultrasonics in stilling wells or bypass gauges. I am told radar functions in either, but I'm not certain, given the limitations of shielding in a stand-off.
Turbulence is now handled quite well by most mfg's.
Foam really affects both technologies. Ultrasonic rarely shoots through foam to the liquid, radar might. No guarantees. It's a trial thing.
Both technologies can be used on liquids and solids. The processing algorithms for liquids and solids are generally different, sometimes
requiring different models, depending on vendor.
Ultrasonics can not shoot through vacuum. Ultrasonics might handle vapors and steam on a case by case basis. I have used ultrasonics on
toluene without difficulty. I found that ultrasonics does not deal well with carbon dioxide (CO2) blankets.
Radar shoots through vacuum without a problem. Radar shoots through vapors without a problem.
In dusty environments: radar now is the way to go, with a caveat for low dielectric materials - like plastics - radar generally shoots right
through plastic, with the always being the tank bottom. Ultrasonics can still handle low dielectric plastics.
For low dielectric liquids magnetostrictive is probably better than either ultrasonic or radar.
One niche specialty of ultrasonics is high accuracy short shots for flow measurement (level of water flowing through a weir or flume).
Like all instrumentation, setup depends on vendor, most have some form local setup - keypad or communicator or PC software. Some are
HART. Some are Profibus. I don't know about FF (Foundation Fieldbus, don't use it).
The Germans seem to be leading the charge in lower cost, good performance industrial radar: Endress & Hauser, Siemens & Ohmart Vega.
Two additional comments:
Tank access ports very near the wall are not suitable because the beam of each technology spreads as it progresses. Access ports towards the center of a tank are desirable for ultrasonic and radar use.
The larger radars are flange mount.
If you are spec'ing tanks, the added cost of a couple nozzles or flanges is incidental to the cost of tank when fabricating a new tank, and can be very useful for level measurement.
Good practice uses a high limit switch with a different technology than the continuous level and the high limit needs access, too.
Dan
Both ultrasonics and radar are top mount, non contact technologies. Ultrasonics is slightly older in commercial use than radar, but the price on radar has dropped in the last 5 years to make it much more common and competitive with ultrasonics. Ultrasonic is now about 5th
generation.
Both technologies can be 2 wire, 2 wire I.S. (intrinsically safe) or EXP (explosion proof) or 4 wire EXP. The long shot devices are 4 wire for power reasons.
All brands have models that come as 4-20mA transmitters. I think all radars are one piece, with no remote mount electronics like ultrasonics can have. Ultrasonics historically has had the ability to have multiple transducers operate from a single electronics box, radar has no such
option. The electronic boxes can have level controllers with relay or analog outputs and digital communications like Modbus. The electronic boxes also typically mount on the ground at eye level, so that operators can keep track with local indication, compared to indicators built into the transmitters themselves, on the top of the tanks, which in many cases are not easily accessible.
Radar's main limitation is found in the dielectric of the material it is shooting. Low dielectrics (good insulators, poor conductors like hydrocarbons) can be problematic for radar. Radar shoots through low dielectrics.
Ultrasonics has a substantial blanking zone directly beneath the transducer/antenna. A radar rod antenna can have an extended length
that is as deep (300mm) as an ultrasonic blanking zone.
When installing a device with a long antenna, one must have sufficient head room above the tank to angle the antenna into the tank. Some
indoor sites with low roofs and high tanks can't handle the installation of a long antenna.
Sometimes tank usage requires a tank level to approach the top of the tank. Radar doesn't operate inside an elevated stand-off, its antenna has to be below the standoff, extended there by a "shield". An ultrasonics
unit is very likely to operate in a reasonably sized stand-off (depends on ratio of diameter to height). This gives ultrasonics a better edge for close-to-the-top level applications, because radar's antenna will extend lower than an ultrasonic transducer in a standoff, even accounting for ultrasonic's
blanking zone.
Both the radar horns and the ultrasonic transducers increase in size for longer distance shots, requiring larger access ports.
Domed top tanks - some radars can't take mounting in the center of a domed top - the parabolic effect of the dome gives them problems.
Both technologies have mixed reactions to dished bottom tanks. Some can handle it, some can't, usually a try-and-see basis.
Radars handle higher pressures, both from a materials/construction perspective and from a technology standpoint. Increased pressures mean
varying ultrasonic velocity rates, with the attendant problem of shifting calibration with shifting pressure. Only radar goes on a pressurized reactor.
Temperature limits are somewhat lower on ultrasonics because of the materials used for the transducer. The horns on radar lend themselves better to high temp functionality, but the electronics still have to located
to where it is cool enough to survive. But I've put radar in hot zones where ultrasonics would have burned up in 3 minutes (had to air purge
cool the transmitter head).
Liquid measurements require the instrument to be plumb, solids measurements frequently make use of some sort of adjustable, tiltable aiming device due to solids' angles of repose.
Both technologies can be fussy about deposits on the transducer or horn. There are photographs circulating that would lead one to believe
otherwise, but I offer a word of warning to wise.
Both technologies cannot be disturbed by nearby inlet streams that intersect their beams.
Both technologies have to deal with obstructions inside tanks: agitators, ladders, eating/cooling coils, baffles ,welds, debris, access ports,
support struts, etc. Some do better than others, not by technology, but by vendor algorithm.
I have used ultrasonics in stilling wells or bypass gauges. I am told radar functions in either, but I'm not certain, given the limitations of shielding in a stand-off.
Turbulence is now handled quite well by most mfg's.
Foam really affects both technologies. Ultrasonic rarely shoots through foam to the liquid, radar might. No guarantees. It's a trial thing.
Both technologies can be used on liquids and solids. The processing algorithms for liquids and solids are generally different, sometimes
requiring different models, depending on vendor.
Ultrasonics can not shoot through vacuum. Ultrasonics might handle vapors and steam on a case by case basis. I have used ultrasonics on
toluene without difficulty. I found that ultrasonics does not deal well with carbon dioxide (CO2) blankets.
Radar shoots through vacuum without a problem. Radar shoots through vapors without a problem.
In dusty environments: radar now is the way to go, with a caveat for low dielectric materials - like plastics - radar generally shoots right
through plastic, with the always being the tank bottom. Ultrasonics can still handle low dielectric plastics.
For low dielectric liquids magnetostrictive is probably better than either ultrasonic or radar.
One niche specialty of ultrasonics is high accuracy short shots for flow measurement (level of water flowing through a weir or flume).
Like all instrumentation, setup depends on vendor, most have some form local setup - keypad or communicator or PC software. Some are
HART. Some are Profibus. I don't know about FF (Foundation Fieldbus, don't use it).
The Germans seem to be leading the charge in lower cost, good performance industrial radar: Endress & Hauser, Siemens & Ohmart Vega.
Two additional comments:
Tank access ports very near the wall are not suitable because the beam of each technology spreads as it progresses. Access ports towards the center of a tank are desirable for ultrasonic and radar use.
The larger radars are flange mount.
If you are spec'ing tanks, the added cost of a couple nozzles or flanges is incidental to the cost of tank when fabricating a new tank, and can be very useful for level measurement.
Good practice uses a high limit switch with a different technology than the continuous level and the high limit needs access, too.
Dan
C
Chris Turcotte
Ultrasonic transmitters use sound while radar transmitters use electromagnetic radiation (similar to light) to measure distance.
Sound transmission is dependent on properties of air; changes to air temperature, pressure, vapors, dust, etc. can affect the readings; radar is almost completely insensitive to air quality. Ultrasonic transmitters will not function at all in a vacuum (there is no air).
Foam and turbulence of the media can present challenges for both technologies, especially ultrasonic (guided-wave radar may be a good choice in such cases).
In general, radar transmitters are more expensive (but can handle more difficult applications), tend to have longer maximum ranges, and often have wider beam angles than ultrasonic transmitters.
You may wish to refer to Magnetrol's Level Technology Comparison or Level Product Selection Guide, which can be found at:
http://www.magnetrol.com/us/html/tech.asp?tech=Tech+Compare
(I am involved with development of level transmitters at Magnetrol, as someone else mentioned, Vega, Endress and Hauser, and also Siemens Milltronics among others provide ultrasonic and radar transmitters as well).
Regards,
Chris Turcotte
Sound transmission is dependent on properties of air; changes to air temperature, pressure, vapors, dust, etc. can affect the readings; radar is almost completely insensitive to air quality. Ultrasonic transmitters will not function at all in a vacuum (there is no air).
Foam and turbulence of the media can present challenges for both technologies, especially ultrasonic (guided-wave radar may be a good choice in such cases).
In general, radar transmitters are more expensive (but can handle more difficult applications), tend to have longer maximum ranges, and often have wider beam angles than ultrasonic transmitters.
You may wish to refer to Magnetrol's Level Technology Comparison or Level Product Selection Guide, which can be found at:
http://www.magnetrol.com/us/html/tech.asp?tech=Tech+Compare
(I am involved with development of level transmitters at Magnetrol, as someone else mentioned, Vega, Endress and Hauser, and also Siemens Milltronics among others provide ultrasonic and radar transmitters as well).
Regards,
Chris Turcotte
Hello Mihir,
E+H published some years ago (2007) a couple of good technical bulletins about this issue
http://instrumentation.eseberri.com/eh-2007-liquid-level-measurement-basics-101/
and also EMERSON in 2013 published a very good guide connected with level measurement.
http://instrumentation.eseberri.com/emerson-2013-the-engineers-guide-to-level-measurement/
I hope you enjoy reading them.
E+H published some years ago (2007) a couple of good technical bulletins about this issue
http://instrumentation.eseberri.com/eh-2007-liquid-level-measurement-basics-101/
and also EMERSON in 2013 published a very good guide connected with level measurement.
http://instrumentation.eseberri.com/emerson-2013-the-engineers-guide-to-level-measurement/
I hope you enjoy reading them.
A
azadkirti
Good informative links. Thanks for sharing.
