Frequently Asked Questions 
Rosemount 3300 Series
Rosemount 5600 Series

General Questions

Why should I use radar technology?

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.

What is the principle of operation?

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.

Are there any restrictions on what still-pipe material can be used?

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.

In what way does the dielectric constant (DC) of the media affect the measurement?

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.

Are radar gauges safe?

Yes. The emitted signal is less than three percent of maximum leakage allowed from a microwave oven. Radar waves are just as safe as 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.

How does the frequency of the radar affect the measurement?

A higher frequency provides a more concentrated narrow 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 vapors, dust and product build up on the antenna. Low frequency radar which have a longer wavelength and wider beam angle and tends to cope better with steam, dust, condensation, contamination and turbulent surfaces.

Does radar work on foam?

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 foam is measured. Low frequency 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 foam is present since the radar uses a lower frequency pulse.

Will two or more radar units in one vessel conflict with each other?

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.

Will radio noise or other interference cause problems?

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 source on the outside.

Are there any restrictions on the nozzle height?

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:  3300 PDS, 5600 PDS, 3300 Manual, 5600 Manual.

Are there any restrictions on the nozzle diameter?

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:  3300 PDS, 5600 PDS, 3300 Manual, 5600 Manual.

3300 Questions

What is the principle of operation for the 3300?

The 3300 Series uses TDR (Time Domain Reflectometry) technology meaning that the transmitter sends out radar pulses. The actual level measurement is a function of the time taken from when the electromagnetic signal is emitted to the time at which the echo from the media is received. Click here for additional principle of operation information.

What is the frequency of the 3300?

When you talk about the frequency of a radar transmitter you normally talk about the carrier-frequency. The 3300 does not use a carrier frequency as non-contacting radars do and therefore it is not relevant to talk about the frequency. This is due to the fact that the 3300 only sends out a pulse which is not modulated.

How to interpret the electrical distance in the tank plot in Radar Configuration Tools (RCT)?

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.

How viscous can the measured media be?

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:

How will coating affect the measurement?

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.

What are the special considerations for interface measurement?

The 3302 can measure both level and interface and the 3301 can measure the interface with fully immersed probe. 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 > 10
• 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.

Can the 3302 measure multiple interfaces?

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

Can the 3302 measure emulsion layers?

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.

Are there special flanges available for replacing displacers?

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.

Will the 3300 see sand in the bottom of a vessel?

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.

Is there any inactive part of the probe?

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 3300 Product Data Sheet, or the 3300 Reference Manual. 

What outputs are available?

Analog 4-20 mA signal with superimposed digital HART signal. A Tri-Loop Converter can be connected to get three additional analog outputs.

How close to the tank wall can the 3300 transmitter be mounted?

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 detailed information please refer to the 3300 Product Data Sheet, or the 3300 Reference Manual.

What are the special considerations when measuring ammonia?

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  Measuring Ammonia with Radar (PDF @125Kb), or Rosemount 3301 successfully used for Level Measurement of Anhydrous Ammonia (PDF @40Kb).  .

Can I get extended length probes that are not shown in the PDS?

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

What pull force will break a flexible single lead probe?

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 diameter 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 more detailed information regarding measurement of solids please refer to  Rosemount 3301 Guided Wave Radar in Solid Level Application.

What is damping unit and what is the default value?

The damping default value is 10 and the unit is seconds. The default value provides a good output current accuracy and stability and as well good response 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 3300 Reference Manual.

Is there a way to use the 3300 Series in Foundation Fieldbus systems?

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.

What measurement error will an incorrect dielectric constant cause in on an interface level?

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

The transmitter is set to burst mode and I can not turn it of. What do I do?

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.

5600 Questions

What is the principle of operation for the 5600?

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. Click here for additional principle of operation information.

What is the frequency of the 5600?

The frequency of the 5600 is 10 GHz.

What outputs are available for the 5600?

How close to the tank wall can the 5600 transmitter be mounted?

The minimum distance 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 5600 Product Data Sheet or the 5600 Reference Manual.

What are the special considerations when measuring ammonia?

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 consult the factory.

What computer communication settings are required with Radar Master?

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

Are there any special considerations when installing in a still-pipe?

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 the factory.

Can I order a flange as part of the model code for the transmitter?

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.

Why do you use windows?

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.

What is the difference between a cone and a horn antenna?

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

Why is there a secondary output on the 5600?

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.

Emerson Process Management, Rosemount Division, 8200 Market Blvd. Chanhassen, MN USA 55317 North America: 1-800-999-9307    International: 952-906-8888  Fax:  952-949-7001

Last Updated 03/25/08 

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