The radar signal is virtually unaffected by the tank content and tank atmosphere, temperature or pressure. The measurement is not influenced by changing material characteristics such as density, dielectric properties and viscosity. Since there are no moving parts the transmitters are virtually maintenance free. All of the characteristics above make radar a very useful and fast growing level measurement technology. 

Radar level measurement technology can be broken down into two different categories; Pulsed and Frequency Modulated Continuous Wave (FMCW). An advantage with Pulsed Technology is that it requires less processing power. Therefore most two-wire gauges use this technology. An advantage with FMCW is that higher accuracy can be achieved but more processing power is required and therefore FMCW-radars are typically four-wire. In Pulsed transmitters the level measurement is a function of the time taken from the radar signal to travel to the surface and back. In FMCW gauges the transmitter constantly emits a swept frequency and the distance is calculated by the difference in frequency of emitted and received signal. 

Yes. The emitted signal is less than three percent of maximum leakage allowed from a microwave oven. Radar waves are of no greater intensity than the constant radio, cellular and other communication waves that surround us every day. Furthermore the transmitter is normally placed in a metallic tank that acts as a Faraday’s cage and therefore the radar waves are isolated within the tank. 
 

With Guided Wave Radar the pulsed microwave are guided down the tank by the probe, making it less sensitive to disturbances than free propagating microwaves. Pulsed Non Contacting Radar uses a carrier frequency, e.g. 6 Hz (5401) or 26 Hz (5402), to carry the microwave which are radiated into the tank with an antenna. 

The microwave pulse is generated in the microwave module. A crystal clock with a Pulse Repetition Frequency (PRF) of 1.8 MHz triggers a pulse generator. A short pulse (1 ns), see picture below, is then generated by fast trnasistors on the pulse generator circuit. The generated pulses are then transferred via the Coupling Net and Out/In to the probe/antenna and into the tank. The reflected microwave is transferred back to the transmitter via the Coupling Net into the Reciever, and then processed by the transmitter logic.

Figure 1 Short pulse created by the pulse generator

Below is a simplified drawing of the 5300 pulse generator. The 5300 has a frequency span of 0.1-2 GHz.

Figure 2 5300 pulse generator

In the 5400 a microwave frequency of 6 GHz or 26 GHz is pulse modulated with the same pulse as in 5300 before the signal goes out to the antenna, see drawing below.

Figure 3 5400 pulse generator 

A higher frequency provides a more concentrated narriw beam which can be useful in applications where there are obstacles present in the tank such as man-ways, agitators or heating coils. The downside of high frequency is that the measurement is more affected by vapours, dust anf product build up on the antenna, Low frequency radar which have a longer wavelength and wider beam angle, tends to cope better with steam, dust, condensation, contamination and turbulent surfaces. 

Electromagnetic energy is emitted from all radar devices. When the emitted signal reaches a point where there is a change in DC, usually the media surface, some of the signal is reflected back to the transmitter. The amount of energy that is reflected back to the transmitter is proportional to the DC of the media. A rule-of-thumb is that the value of the dielectric constant represents the percentage of energy that is reflected. Thus a DC of eight means that eight percent of the emitted energy is reflected back to the transmitter. Fundamentally media with a higher DC provide stronger return signals and are therefore easier to measure. 

The effects of foam on a radar measurement can be difficult to predict. In some applications the foam may dampen out the signal completely while other types of foam may be transparent to the transmitter. The thickness, density and the dielectric constant are factors that need to be considered when evaluating an application with foam.

On dry foam the microwaves typically passes through and detects the liquid surface below. On medium type foam the signal can be absorbed or scattered and the results are therefore hard to predict. If the foam is wet the microwaves are often reflected from the foam surface and thereby the foam surface level is measured.

The frequency at which the radar operates also affects how fowm is measured. Low ferquency radar (5 GHz) in general penetrates foam to a larger extent than high frequency (20 GHz) radar. Guided Wave Radar is in general better suited to measure on applications where foram is present, sinc ethe radar uses a lower frequency pulse, e.g. 5300 0.1-2 GHz. 

Any type of conductive material can be used as long as it is compatible with the process media. If the material is not conductive it will be transparent to the radar-beams and therefore it will have no affect. 

The signals from two or more transmitters in one tank will not blend and therefore the radar units will not conflict with each other. If it concerns two or more 3300s the rules for nearby objects would apply to the probes as they do to other metallic objects nearby. For that reason the probes need to be installed a certain distance away from each other. 

The transmitters use a specific narrow frequency and are therefore not prone to disturbances from other sources. It is very uncommon with disturbances and it is rare that the disturbance source operates at precisely the same frequency as the transmitter.

Furthermore, the transmitters are often installed in metallic tanks that provide a Faraday's cage which prevents electromagnetic disturbances from the outside to enter the tank.

With Guided Wave Radar, if disturbances are present in tank the coaxial probe are recommended, since the radar signal travels inside of the pipe undisturbed by the interference sources on the outside. 

Since the nozzle, and especially the lower end of the nozzle, can create interfering echoes it is recommended that the height of the nozzle is kept within certain values depending on the type of probe / antenna and type of transmitter that is used. For detailed information regarding these values please refer to the Product Data Sheet and Reference Manual for each transmitter. 

In conjunction with the above statement, the nozzle diameter also affects the measurement,since a diameter nozzle that is too small will create disturbance echoes. For detailed information regarding these values please refer to the Product Data Sheet and Reference Manual for each transmitter. 

Pipes should be an all-metal material. Non-metallic pipes or sections are not recommended for non-contacting radar. Plastic, plexiglas, or other non-metal materials do not shield the radar from outside disturbances and offer minimal, if any, application benefit. Other requirements include:

• Pipe should have a constant inside diameter
• Pipe must be smooth on the inside (smooth pipe joints are acceptable, but may reduce accuracy)
• Avoid deposits, rust, gaps and slots
• One hole above the product surface
• Minimum hole diameter is 0.25 in. (6 mm)
• Hole diameter (Ø) should not exceed 10% of the pipe diameter (D)
• Minimum distance between holes is 6 in. (150 mm) (1)
• Holes should be drilled on one side and de-burred
• Ball valve or other full valves must be completely open

Failure to follow these requirements may affect the reliability of the level measurement. See Technical note, 00840-0300-4024, Guidelines for Choosing and Installing Radar in Stilling Wells and Pipes, for more information. 

n some applications with high temperatures, or in highly corrosive environment, the probes or antennas need to be made out of exotic materials that can be stand the material stress. Rosemount offers two different exotic materials as standards:

• Alloy 400
• C-276

For more details about material structure, other exotic materials, pricing or other questions regarding exotics - please consult factory. 

Basic configuration can easily be done either with Rosemount RadarMaster, a Rosemount 375 Field Communicator, the AMS™ Suite, DeltaV® or any other DD (Device Description) compatible host system. For advanced configuration features and extensive diagnostics, RadarMaster, or an alternative host that supports enhanced EDDL (such as the AMS Device Manager) is required. Rosemount RadarMaster is shipped with every transmitter but it is also possible to download RadarMaster or other DD's on Rosemount.com

RadarMaster is a user-friendly, Widnows based software package that provides easy configuration and service for both FOUDATION™ filedbus and HART®. A wizard guides the user to enter the required parameters for a basic configuration. "Measure & learn" functionality is accessed through Radarmaster. It enables automatic suggestion of level threshold values, therebymaking tough applications easy to configure. RadarMaster also includes an echo curve with movie featur, off-line configuration, logging and extensive on-line help.

The Enhanced EDDL capabilities of the Rosemount Radars also make it possible to view the echo curve from a field communicator or AMS, and to initiate the Measure-and-Learn functionality in the transmitter. 

The 3300 & 5300 series uses TDR (Time Doamin Reflectometry) technology meaning that the transmitter sends out radar pulses. The actual level measurement is a fucntion of the time taken from when the electromagnetic signal is emitted to the time at which the echo from the media is received. For more general information regarding the principle of operation please refer to What is the principle of operation under General Questions. 

When you talk about the frequency of a radar transmitter you normally talk about the carrier-frequency. Guided wave radar's does not use a carrier frequency as non-contating radars do and therefore it is not relevant to talk about the frequency. This is due to the fact that GWR only sends out a pulse which is not modulated. 

The electrical distance that is shown on the x-axis of the tank plot is used when comparing the distance measured by the transmitter and the real distance. Due to the influence from the dielectric properties on the wave propagation speed the electrical distance values have to be adjusted when the wave is not traveling through air. The electrical length shows the distance with the assumption that the wave travels in air. Practically this means that the distance to the first level peak will have the same electrical distance and real distance. When the waves continues down through the media the real length from the surface to the end of the probe or to the interface level can be calculated through the formula below:

In conclusion the distance to the upper product can be read straight from the plot while the interface distance has to be calculated using the formulae above. 

The different probes have different max limits regarding the viscosity of the measured media. The single probes are more suitable for high viscosity media while the coax probe can be used on low viscosity media. The guidelines for the different probes and examples of viscosity are presented below:

If coating forms on the probe the measured signal will be weaker. If the media itself has a high dielectric constant some coating is not much concern but 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 cause bridging between the two leads and this will create false echoes that can lead the transmitter to interpret a bridge as the actual level. Single lead is recommended in coating applications.

Coating can cause an accuracy influence. Maximum error due to coating is 1-10% depending on probe type, dielectric constant, coating thickness and coating height above product surface. 

The 3302 can measure both level and interface and the 3301 can measure the interface with fully immersed probe. Rosemount 5302 is the ideal choice for measuring the level of oil, and the interface of oil and water, or other liquids with significant dielectric differences. Rosemount 5301 can also be used in applications where the probe is fully submerged in the liquid. However, for interface measurement a few criteria have to be fulfilled:

• The dielectric of the upper product must be known and should not 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 upper product > 10 cm (4 in.) for coax, rigid twin and rigid single probes and 20 cm (8 in) for flexible twin probes in order to be detected
• The max measuring range is limited by the upper product dielectric constant
• Coaxial, Twin probes or rigid single can be used
• Max upper product DC is 5 for twin lead probes and 10 for coaxial probe

Target applications include interfaces between oil/oil-like (DC < 3) and water/water-like liquids (DC > 20). Consult factory regarding other interface applications and when emulsion layer!

Note that in order to use the 3301 for interface applications the probe has to be fully immersed at all times. This since the calculations are based on a full tank and if there will be errors in the interface level. The normal 3A coaxial probe without holes can be used since there is a hole near the flange where the liquid can flow through. This hole has to be immersed in the upper liquid otherwise there will be measurement errors. The software compensates for the air gap that is present between the flange and the hole in the probe. 

No. The 3302 and 5302 can measure the surface layer and one liquid/liquid interface. The criteria for interface measurement as stated above must be fulfilled.

Emulsion layers are in general hard to predict and there are three main types of layers:

1. DC of top layer and emulsion layer is similar (difference in dielectric constant < 10). In this case the interface level as reported by the transmitter will be the bottom of the emulsion layer.
2. DC of bottom layer and emulsion layer is similar (difference in dielectric constant between top layer and emulsion layer > 10). In this case the interface level as reported by the transmitter will be the top of the emulsion layer.
3. There is a linear transition in DC from the bottom to the top of the emulsion layer. In this case it is hard to predict where the reported interface level is. If the linear transition is over a long distance there is a risk that no interface echo is reflected back to the transmitter since the reflecting pulse is created when there is a distinct change in DC. If a linear oil water interface is very thin (< 10 cm) the transmitter would probably give a good signal from the interface since the emulsion is so thin and the difference in dielectrics between oil and water is large. It is difficult to say though where the transmitter will report the interface level. It can report the top of, the bottom of, or somewhere within, the emulsion layer.

Yes. Masoneilan and Fisher 249B and 249C displacer flanges are available. The code for Masoneilan is TM, the code for Fisher 249B is TF, and the code for Fisher 249C is TT. 

No. Since the sand will be embedded in water which is a high dielectric media (DC~80) the transmitter will only see the water. The same is true for all media that are embedded in water. 

The active measuring range is reduced by the upper and lower dead zones. The upper dead zone is the minimum distance from the reference point to the product surface. The measuring range is also reduced in the end of the probe by the lower dead zone. How large the upper and lower dead zones are depend on probe type and the dielectric constant of the measured media. For details please refer to the Product Data Sheet (3300 and 5300), or the Reference Manual for Rosemount 3300 or 5300 Series. 

Measurement data is transmitted as an analog mA signal with a superimposed digital HART® signal (3300/5300) or FOUDATION™ filedbus signal (5300). The HART® signal can be used in multidrop mode. By sending the digital HART® signal to the optional HART® Tri-loop, it is possible to have up to three additional 4-20 mA analog signals. Modbus communication is also available for 3300. 

Like the nozzle the tank wall can also affect the measurement through disturbance echoes. The minimum distance to the tank wall is the same as the distance to any disturbing object that may be present in the tank. If there are obstacles present in the tank the coaxial probe is the best probe to use. If the tank wall is metallic and smooth the probe can be mounted closer to the wall. For details please refer to the Product Data Sheet (3300 and 5300), or the Reference Manual for Rosemount 3300 or 5300 Series. 

Tanks with anhydrous ammonia have a heavy vapor above the surface that attenuates the signal from the radar transmitter. A higher pressure in the tank will cause a more attenuated signal. A special formula is therefore used to evaluate what the maximum measuring range is in anhydrous ammonia as a function of the pressure in the tank:

Note that, when measuring hydrous (aqueous) ammonia, this formula does not apply. For more detailed information regarding measurement of ammonia please refer to ammonia technical note available on the Value Selling Matrix. A dynamic Vapor Compensatio-probe can now be ordered as standard together with the rosemount 5300 Series transmitter. Developed to give better opeation in liquid gas applications such as LPG, NGL and ammonia. 

For some applications it can possible to use longer rigid probes than what is shown in the PDS. Consult factory in such cases. 

In solid application, media might cause down-pull forces on silo roofs. The silo roof must be able to withstand the probe collapse load or at least the maximum probe tensile load. The tensile load depends on the silo size, material density, and the friction coefficient. Forces increase with the buried length, the silo and probe diameter. In critical cases, such as for products with a riskfor build-up, it is better to use a 0.24 in (6 mm) probe. Depending on their position, forces on probes are generally two or ten times greater on probes with tie-down than on probes with ballast weights.

For the 0.16 inch (4 mm) in diameter cable the tensile strength is 2698 lb (12 kN) and the collapse load is 3597 lb (16 kN). For the 0.24 inch (6 mm) in diamater cable the tensile strength is 6744 lb (29 kN) and the collapse load is 7868 lb (35 (kN). The 0.24 inch (6 mm) is only offered as a special at this time, consult factory. For calculation of tensile load the Tensile Load calculator (see Products > Configurers and Tools) can be used for guidance.

Note:

Abrasive medica can wear out the probe. Consider using non-contacting radar. For more detailed information regarding measurement of solids please refer to the solids technical note available in the Application Library on Level Web and on the Value Selling Matrix. 

The damping default value is 10 for 3300 Series and 2 for the 5300 Series. The unit is seconds. The default value provides a good output current accuracy and stability and as well good reponse time. The damping can be set to a lower or higher value if the application needs it, for example rapid level changes. For more information see the Reference Manual. 

It is possible to use the Rosemount 848T as a converter from HART to FF. You will not be able to do any advanced configuration but you will be able to read the primary variable, look at the status, set hi and low alarms and some other standard FF functions through the AI block. 

Errors due to changes in the medium’s dielectric values can be significant. It is calculated by:

For example, if the physical thickness is 20” (51 cm) and dielectric varies from 2 to 4:

In order to turn off the burst mode the transmit and receive buffers must be set to one. This is done according to instructions below:

1. Right click on My Computer and choose Properties
2. Choose the tab Hardware
3. Click on the button Device Manager
4. Navigate to Ports in the list of hardware
5. Right click on Serial Port COM 1 and choose Properties
6. Choose the tab Port Settings
7. Click Advanced
8. Drag the slider for Receive Buffer and Transmit Buffer to 1
9. Click OK
10. Reboot Computer
11. Repeat for COM 2 if available

When installing Radar Configuration Tools there is a warning recommending changing the com port buffers with instructions how to do so. 

The 5600 Series uses FMCW technology. The transmitter constantly emits a swept frequency signal and the distance is calculated by the difference in frequency between the emitted and received signal at any point in time. One advantage with FMCW is that higher accuracy can be achieved. For more general information regarding the principle operation please refer to What is the principle of operation under General Questions.

The 5400 Series uses Pulsed, free propagating radar. The level of the liquid is measured by short radar pulses which are transmitted from the antenna at the tank top towards the liquid. When a radar pulse reaches a media with a different dielectric constant, part of the energy is reflected back to the transmitter. The time difference between the transmitted and the reflected pulse is proportional to the distance, from which the level is calculated. 

The minimumdistance to the tank wall depends on which antenna is used. With a more concentrated beam (larger antenna), the closer to the tank wall the device can be mounted. For detailed information please refer to the Reference Manual or Product Data Sheet. 

Tanks with anhydrous ammonia have a heavy vapor above the surface that attenuates the signal from the radar transmitter. A higher pressure in the tank will cause a more attenuated signal. A special formula is therefore used to evaluate what the maximum measuring range is in anhydrous ammonia as a function of the pressure in the tank. For the 5600 the formula is:

Note that, when measuring hydrous (aqueous) ammonia, this formula does not apply. Hydrous ammonia has a high dielectric constant and therefore provides good reflection. For more detailed information regarding measurement of ammonia please refer to the ammonia technical note available in the Application Library and on the Value Selling Matrix. 

In order to achieve communication with the 5600 the transmit buffers and the receive buffers have to be set to one. These buffers are initially set to 15 by default on Windows 2000 and Windows XP. To change the buffer settings follow the instructions below:

1. Right click on My Computer and choose Properties
2. Choose the tab Hardware
3. Click on the button Device Manager
4. Navigate to Ports in the list of hardware
5. Right click on Serial Port COM 1 and choose Properties
6. Choose the tab Port Settings
7. Click Advanced
8. Drag the slider for Receive Buffer and Transmit Buffer to 1
9. Click OK
10. Reboot Computer
11. Repeat for COM 2 if available

Installing in a still-pipe can be used either when the existing tank connection includes a stilling well or when the measurement is improved by measuring inside a pipe instead of outside. The cone antenna is used for still-pipe measurements and it is important that the size of the antenna match the size of the pipe. For optimal accuracy the inside of the pipe must be clean and free from deposit, rust, gaps ,slots etc. The largest pipe / antenna that can be used is 6". For larger diameter pipes the 5600 Series should not be used. For more detailed information on measurement in still-pipes please consult factory or refer to the Technical Note Rosemount 5601 Radar Level Transmitter in Stilling Well Applications or Guidelines for Choosing and Installing Radar in Stilling Wells and bypass Chambers, which you will find in the Application Library on the Value Selling Matrix.  

Flanges for the 5601 should be ordered as separate line items for all antennas except the Process Seal antenna and the Cone antenna with Integrated Flushing Connection. For these antennas the flanges are included in the model code. The process seal has a non-welded flange and the Cone antenna with Integrated Flushing Connection has a welded flange. 

To isolate electronics from process in tank such as vapour and corrosion. The Process Seal antenna has a PTFE window. It is an all PTFE antenna (all materials exposed to tank atmosphere are PTFE). Due to the smooth surface of the window and the non-sticky nature of PTFE it can be used on some hygienic applications. 

It is just different names for the same type of antenna. 

The secondary output option gives an additional 4-20 mA analog output that for example can be used for a local display or alarm handling or to track the signal to noise ratio.