Interview Questions.

Question 1. What Is The Principle Of Operation Of Guided Wave Radar ?

Answer :

Radar degree measurement era may be broken down into two exceptional categories; Pulsed and Frequency Modulated Continuous Wave (FMCW). An gain with Pulsed Technology is that it calls for much less processing power. Therefore most -twine gauges use this technology. An gain with FMCW is that higher accuracy can be achieved but extra processing electricity is needed and therefore FMCW-radars are generally 4-cord. In Pulsed transmitters the level dimension is a function of the time taken from the radar sign to tour to the surface and lower back. In FMCW gauges the transmitter constantly emits a swept frequency and the gap is calculated by using the distinction in frequency of emitted and received sign.

Question 2. Are Radar Gauges Safe?

Answer :

Yes. The emitted signal is much less than 3 percent of most leakage allowed from a microwave oven. Radar waves are of no more depth than the constant radio, mobile and different verbal exchange waves that surround us every day. Furthermore the transmitter is generally placed in a metallic tank that acts as a Faraday’s cage and therefore the radar waves are isolated inside the tank.

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Question 3. What Is The Difference In Frequency Between Pulsed Technology Guided Wave Radar And Non Contacting Radar?

Answer :

With Guided Wave Radar the pulsed microwave are guided down the tank by way of the probe, making it much less sensitive to disturbances than loose propagating microwaves. Pulsed Non Contacting Radar makes use of a carrier frequency, e.G. 6 Hz (5401-rosemount) or 26 Hz (5402 – rosemount), to carry the microwave which are radiated into the tank with an antenna.

Question four. Why Should We Use Radar Technology?

Answer :

The radar signal is without a doubt unaffected via the tank content and tank surroundings, temperature or pressure. The measurement isn't always prompted by changing fabric traits such as density, dielectric properties and viscosity. Since there aren't any transferring elements the transmitters are simply protection free. All of the characteristics above make radar a totally useful and fast growing stage dimension generation.

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Question five. How Does The Frequency Of The Radar Affect The Measurement?

Answer :

A higher frequency gives a greater focused slim beam which may be useful in applications wherein there are obstacles present within the tank inclusive of man-ways, agitators or heating coils. The disadvantage of high frequency is that the size is extra affected by vapours, dust and product building up on the antenna, Low frequency radar which have an extended wavelength and wider beam attitude, has a tendency to cope better with steam, dirt, condensation, contamination and turbulent surfaces.

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Question 6. In What Way Does The Dielectric Constant (dc) Of The Media Affect The Measurement?

Answer :

Electromagnetic energy is emitted from all radar devices. When the emitted sign reaches a factor where there is a alternate in DC, typically the media surface, a number of the signal is reflected back to the transmitter. The amount of electricity that is reflected back to the transmitter is proportional to the DC of the media. A rule-of-thumb is that the fee of the dielectric consistent represents the proportion of energy that is reflected. Thus a DC of eight manner that eight percent of the emitted strength is pondered lower back to the transmitter. Fundamentally media with a better DC offer more potent return alerts and are consequently simpler to measure.

Question 7. Does Radar Work On Foam?

Answer :

The consequences of foam on a radar measurement can be tough to are expecting. In some packages the foam can also dampen out the signal absolutely while different types of foam can be obvious to the transmitter. The thickness, density and the dielectric consistent are elements that need to be considered whilst comparing an utility with foam.

On dry foam the microwaves generally passes via and detects the liquid surface under. On medium type foam the signal can be absorbed or scattered and the outcomes are therefore tough to expect. If the froth is moist the microwaves are regularly contemplated from the foam floor and thereby the foam surface level is measured.

The frequency at which the radar operates also influences how fowm is measured. Low ferquency radar (5 GHz) in general penetrates foam to a larger extent than excessive frequency (20 GHz) radar. Guided Wave Radar is in trendy better suitable to measure on applications where foram is present, sinc ethe radar uses a decrease frequency pulse.

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Question eight. Are There Any Restrictions On What Still-pipe Material Can Be Used?

Answer :

Any sort of conductive material may be used as long as it's miles compatible with the method media. If the cloth isn't always conductive it'll be obvious to the radar-beams and consequently it'll don't have any affect.

Question nine. Will Two Or More Radar Units In One Vessel Conflict With Each Other?

Answer :

The alerts from  or extra transmitters in one tank will no longer combo and consequently the radar units will now not warfare with every different. If it concerns  or extra 3300s the guidelines for close by objects would apply to the probes as they do to other metallic gadgets close by. For that motive the probes need to be mounted a sure distance away from every different.

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Question 10. Will Radio Noise Or Other Interference Cause Problems?

Answer :

The transmitters use a particular slim frequency and are consequently no longer at risk of disturbances from different assets. It may be very uncommon with disturbances and it's far rare that the disturbance supply operates at precisely the identical frequency as the transmitter. Furthermore, the transmitters are frequently hooked up in metal tanks that offer a Faraday’s cage which prevents electromagnetic disturbances from the out of doors to go into the tank. With Guided Wave Radar, if disturbances are found in tank the coaxial probe are recommended, for the reason that radar signal travels interior of the pipe undisturbed by way of the interference resources at the out of doors.

Question eleven. Are There Any Restrictions On The Nozzle Height?

Answer :

Since the nozzle, and specially the lower give up of the nozzle, can create interfering echoes it's far endorsed that the height of the nozzle is kept inside positive values relying at the sort of probe / antenna and kind of transmitter that is used. For precise records regarding those values please confer with the Product Data Sheet and Reference Manual for each transmitter.

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Question 12. Are There Any Restrictions On The Nozzle Diameter?

Answer :

In conjunction with the above announcement, the nozzle diameter additionally affects the size,considering a diameter nozzle that is too small will create disturbance echoes. For particular records regarding those values please refer to the Product Data Sheet and Reference Manual for each transmitter.

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Question 13. Are There Any Restrictions When Measuring In Stilling Pipes?

Answer :

Pipes ought to be an all-metal fabric. Non-metal pipes or sections aren't recommended for non-contacting radar. Plastic, plexiglas, or different non-metallic materials do no longer protect the radar from outdoor disturbances and provide minimal, if any, utility gain.

Other requirements consist of:

    Pipe should have a regular inner diameter
    Pipe should be easy on the interior (clean pipe joints are suitable, but may additionally lessen accuracy)
    Avoid deposits, rust, gaps and slots
    One hollow above the product surface
    Minimum hollow diameter is 0.25 in. (6 mm)
    Hole diameter (Ø) ought to now not exceed 10% of the pipe diameter (D)
    Minimum distance among holes is 6 in. (one hundred fifty mm) (1)
    Holes need to be drilled on one facet and de-burred
    Ball valve or other complete valves must be completely open

Failure to follow those requirements may also have an effect on the reliability of the extent dimension. See Technical observe, 00840-0300-4024, Guidelines for Choosing and Installing Radar in Stilling Wells and Pipes, for extra facts.

Question 14. What Is Purpose Of Exotic Materials?

Answer :

In a few programs with excessive temperatures, or in fairly corrosive surroundings, the probes or antennas want to be made out of wonderful materials that can be stand the cloth strain. Rosemount gives two extraordinary individual substances as standards.

Question 15. What Is Eddl & Dd’s? And How Do They Affect Configuration Tools And Host Systems?

Answer :

Basic configuration can easily be completed both with Rosemount RadarMaster, a Rosemount 375 Field Communicator, the AMS™ Suite, DeltaV® or any other DD (Device Description) compatible host gadget. For superior configuration functions and extensive diagnostics, RadarMaster, or an opportunity host that helps stronger EDDL (which includes the AMS Device Manager) is required. Rosemount RadarMaster is shipped with each transmitter but it's also viable to download RadarMaster or other DD’s on Rosemount.Com RadarMaster is a consumer-friendly, Widnows based totally software package that offers easy configuration and provider for each FOUDATION™ filedbus and HART®. A wizard publications the person to go into the desired parameters for a basic configuration. “Measure & examine” functionality is accessed thru Radarmaster. It permits automatic idea of level threshold values, therebymaking hard packages easy to configure. RadarMaster additionally includes an echo curve with movie featur, off-line configuration, logging and sizeable on line help. The Enhanced EDDL skills of the Rosemount Radars also make it possible to view the echo curve from a area communicator or AMS, and to initiate the Measure-and-Learn functionality within the transmitter.

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Question 16. How Will Coating Affect The Measurement?

Answer :

If coating paperwork at the probe the measured sign will be weaker. If the media itself has a high dielectric consistent a few coating isn't always a good deal issue however if it is a low DC media coating can be a problem. If a twin probe or a coaxial probe is used the coating can motive bridging among the 2 leads and this may create fake echoes that may lead the transmitter to interpret a bridge as the real level. Single lead is suggested in coating applications. Coating can motive an accuracy affect. Maximum mistakes due to coating is 1-10% depending on probe kind, dielectric consistent, coating thickness and coating top above product floor.

Question 17. What Are The Special Considerations For Interface Measurement?

Answer :

For interface measurement a few criteria must be fulfilled:

    The dielectric of the top product must be recognized and should no longer vary.
    Upper product dielectric < Lower product dielectric
    Difference between dielectrics depends on the upper product thickness, but a guideline is > 10(3300) > 6(5300)
    Thickness of higher product > 10 cm (four in.) for coax, rigid twin and rigid single probes and 20 cm (8 in) for bendy dual probes as a way to be detected
    The max measuring variety is restricted by way of the higher product dielectric consistent
    Coaxial, Twin probes or inflexible unmarried may be used
    Max top product DC is five for twin lead probes and 10 for coaxial probe
    Target programs encompass interfaces between oil/oil-like (DC < 3) and water/water-like liquids (DC > 20). Consult manufacturing facility concerning different interface packages and while emulsion layer!

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Question 18. Can Guided Wave Radar Measure Emulsion Layers?

Answer :

Emulsion layers are in wellknown tough to expect and there are three main kinds of layers:

DC of pinnacle layer and emulsion layer is comparable (distinction in dielectric regular < 10). In this case the interface level as reported by the transmitter will be the bottom of the emulsion layer.

DC of bottom layer and emulsion layer is similar (difference in dielectric constant between top layer and emulsion layer > 10). In this example the interface level as mentioned via the transmitter will be the top of the emulsion layer.

There is a linear transition in DC from the lowest to the pinnacle of the emulsion layer. In this case it's miles difficult to are expecting where the said interface stage is. If the linear transition is over an extended distance there may be a chance that no interface echo is contemplated again to the transmitter since the reflecting pulse is created while there may be a wonderful exchange in DC. If a linear oil water interface may be very skinny (< 10 cm) the transmitter might in all likelihood supply an excellent signal from the interface since the emulsion is so thin and the difference in dielectrics among oil and water is huge. It is hard to mention even though wherein the transmitter will report the interface stage. It can file the pinnacle of, the bottom of, or someplace within, the emulsion layer.

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Question 19. Will The Guided Wave Radar See Sand In The Bottom Of A Vessel?

Answer :

No. Since the sand will be embedded in water which is a excessive dielectric media (DC~80) the transmitter will simplest see the water. The identical is actual for all media which are embedded in water.

Question 20. Is There Any Inactive Part Of The Probe?

Answer :

The active measuring range is decreased by the higher and decrease useless zones. The upper dead area is the minimal distance from the reference point to the product floor. The measuring range is also decreased in the long run of the probe via the lower dead zone. How massive the higher and decrease lifeless zones are depend upon probe kind and the dielectric constant of the measured media.

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Question 21. How Close To The Tank Wall Can The Probe Be Mounted?

Answer :

Like the nozzle the tank wall also can affect the dimension through disturbance echoes. The minimal distance to the tank wall is similar to the space to any annoying object that can be gift inside the tank. If there are barriers gift within the tank the coaxial probe is the first-class probe to apply. If the tank wall is steel and easy the probe can be established towards the wall.

Question 22. What Pull Force Will Break A Flexible Single Lead Probe?

Answer :

In stable utility, media may cause down-pull forces on silo roofs. The silo roof need to be capable of face up to the probe fall apart load or at the least the maximum probe tensile load. The tensile load relies upon at the silo length, fabric density, and the friction coefficient. Forces increase with the buried length, the silo and probe diameter. In critical cases, such as for merchandise with a riskfor construct-up, it's miles better to apply a 0.24 in (6 mm) probe. Depending on their position, forces on probes are typically two or ten times greater on probes with tie-down than on probes with ballast weights.

Question 23. What Is The Principle Of Operation For Non Contacting Radars?

Answer :

The 5600 Series makes use of FMCW generation. The transmitter continuously emits a swept frequency signal and the gap is calculated through the distinction in frequency between the emitted and obtained signal at any factor in time. One gain with FMCW is that higher accuracy can be accomplished. For greater preferred information concerning the principle operation please talk to What is the precept of operation under General Questions. The 5400 Series uses Pulsed, unfastened propagating radar. The degree of the liquid is measured by way of quick radar pulses which are transmitted from the antenna at the tank top in the direction of the liquid. When a radar pulse reaches a media with a one-of-a-kind dielectric steady, a part of the energy is reflected again to the transmitter. The time distinction among the transmitted and the pondered pulse is proportional to the gap, from which the level is calculated.

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Question 24. How Close To The Tank Wall Can The Non Contacting Transmitter Be Mounted?

Answer :

The minimum distance to the tank wall depends on which antenna is used. With a more focused beam (larger antenna), the toward the tank wall the device can be established.

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Question 25. Why Do You Use Process Seal Antennas?

Answer :

To isolate electronics from manner in tank consisting of vapour and corrosion. The Process Seal antenna has a PTFE window. It is an all PTFE antenna (all substances exposed to tank environment are PTFE). Due to the easy surface of the window and the non-sticky nature of PTFE it can be used on some hygienic programs.

Question 26. What Is The Difference Between A Cone And A Horn Antenna?

Answer :

It is just special names for the identical form of antenna.