Coaxial Probe Guided Wave Radar Level Transmitter is used to measure&control liquid with low permittivity. Contact measurement.

SIRD-704 Coaxial Probe Guided Wave Radar Level Sensor

Guided wave radar level transmitters equipped with Coaxial Probe are used in liquids. Especially liquids with low dielectric constant. For example: non-ionized water, deoxygenated water and other liquid measurement. If the dielectric constant of the liquid is too low, radar level sensors are not suitable. Coaxial Probe Guided Wave Radar Level Transmitter can measure and control the level of liquids with low electrical constants or surface fluctuations. Signal output (4~20) mA/HART.

Sino-Inst offers a variety of Guided wave radar Level Sensors for industrial level measurement. If you have any questions, please contact our sales engineers.

Features of Coaxial Probe Guided Wave Radar Level Transmitter

  1. Applicable medium: liquid. Especially liquid with low dielectric constant. It can measure any medium with a dielectric constant greater than or equal to 1.4.
  2. Generally used to measure the medium with viscosity ≤ 500cst and not easy to produce adhesion.
  3. The maximum range of rod radar can reach 6 meters.
  4. It has a strong ability to inhibit steam and foam, and the measurement is not affected.
  5. For liquid materials with a relatively small dielectric constant. A double probe type measurement method can be used to ensure good and accurate measurement.

Specifications of Coaxial Probe Guided Wave Radar Level Transmitter

Applicable medium:Liquid, especially liquid with low dielectric constant
Should use:Measurement of non-ionized water, deoxidized water, and other liquids
Explosion-proof certification:Exia IIC T6 Ga/ Exd IIC T6 Gb
Measuring range:6m
Frequency rate:500MHz-1.8GHz
Day Line:Coaxial tube antenna
measurement accuracy:±5mm
Process temperature:-40~130℃(standard type)/-40~250℃(high-temperature type)
Process pressure:(-0.1~4)MPa
Signal output:(4~20)mA/HART
On-site display:Four-digit LCD programmable
power supply:Two-wire system (DC24V)/Four-wire system (DC24V/AC220V)
Outer shell:aluminum single cavity/aluminum dual cavity/plastic/stainless steel single cavity
Process connection:Thread/flange (optional)

Extended Reading: Influence of Dielectric Constant on Liquid Level Measurement | Radar-Guided Wave Radar Level Meter

Guided Wave Radar Level Transmitter Antenna

Guided Wave Radar Level Transmitter transmits and receives electromagnetic waves through guided wave metal or cable, which is a contact measurement. Because it has little effect on dust, steam, and the adhering medium on the probe, it is more widely used in solid material level and liquid level measurement with a small dielectric constant.

The dual-cable guided wave radar level sensor uses the change of measuring capacitance to measure the level of the liquid level. The medium between the two electrodes is the liquid and the gas above it. It is suitable for liquid level measurement of corrosive and high-pressure media . Fundamentally solve the influence of temperature, humidity, pressure, conductivity of materials and other factors on the measurement process. Therefore, it has extremely high anti-interference and reliability

Guided wave radar level sensor equipped with a coaxial tube probe. It is used for level measurement and control of liquids with low dielectric constant or fluctuating surface. If the dielectric constant of the measured material is Too low. General types of radar level sensors are not suitable.

Extended reading: GWR Solid Level Sensor-for Cement silo-Ash powder measure

Guided Wave Radar Level Transmitter Working Principle

High-frequency microwave pulses from guided wave radar propagate along the detection component (steel cable or steel rod). When encountering the measured medium. Due to a sudden change in the dielectric constant, it causes reflection. A part of the pulse energy is reflected back. The time interval between the transmitted pulse and the reflected pulse is proportional to the distance of the measured medium.

Guided wave radar is a measuring instrument based on the principle of time travel. The radar wave runs at the speed of light. The running time can be converted into a level signal by electronic components. The probe emits high-frequency pulses and propagates along the cable or rod probe. When the pulse meets the surface of the material, it is reflected back and received by the receiver in the instrument, and the distance signal is converted into a level signal.

The reflected pulse signal is transmitted to the electronic circuit part of the instrument along the cable or rod probe. The microprocessor processes this signal. Identifies the echo generated by the microwave pulse on the surface of the material. The correct echo signal identification is done by the pulse software.

Guided Wave Radar Level Sensor Working Principle.png
Guided wave radar liquid level measurement calculation formula

The distance D from the surface of the material is proportional to the time travel T of the pulse:


Where C is the speed of lightSince the distance E of the empty tank is known, the level L is:


Set by inputting empty tank height E (=zero point), full tank height F (=full scale) and some application parameters. The application parameters will automatically adapt the instrument to the measurement environment. Corresponding to 4-20mA output.

The technical video from Endress+Hauser USA explains the Measuring Principle Guided Radar with Time-of-Flight very well. Let’s look together.

Video source:

Guided Wave Radar Level Transmitter Principle of Operation

Each component of the radar level gauge has its function and role. When using it, use it in strict accordance with the requirements. Among them, the waveguide of the radar level gauge is a component that needs to pay more attention to every detail when using it. Next, the operation items of the still-pipe of the radar level gauge will be explained:

  1. The minimum survey scale is related to the receiving antenna.
  2. For overfill protection, a non-hazardous interval can be defined and added to the blind zone.
  3. If the medium has a low dielectric constant, the bottom of the tank is visible when it is at a low liquid level. This is to ensure the accuracy of the survey.
  4. In practice, it is possible for the guided wave radar level gauge to survey the tip of the receiving antenna. However, consider the impact of erosion and paste. The final value of the survey scale should be at least 100mm apart from the tip of the receiving antenna.
  5. Depending on the concentration of the liquid, the foam can not only condense microwaves, but also reflect them. However, surveys can be performed under certain conditions.
  6. The survey scale starts from the point where the beam involves the bottom of the tank. But in other conditions, if the tank is concave or tapered, there is no way to conduct surveys when the level is below this point.
  7. Radar level gauge has its requirements for stilling wave tube during installation. It is required that the inner diameter of the still-pipe is equal to 102.3 mm, the wall thickness is 6 mm, and the vertical deviation of the installation requires less than +/-0.5 degrees.
  8. A support frame must be made at the bottom of the radar level gauge, and the gap between it and the still-wave tube is 15-30 mm. To reduce the impact of turbulence during feeding, the bottom of the still need to install a reflector and check ring.
  9. The inner wall of stilling wave tube shall be smooth and free of burrs. And every 500 mm apart need to drill a 20 mm inner diameter balance hole. The eccentricity of the balance hole is within 0.5 degrees. Moreover, the welding of the waveguide section and the section is a sleeve welding method. The gap is less than 1 mm. The eccentricity is within 1 degree. The straightness is within 0.5:100.

Extended reading: Radar Level Meter for Corrosive Liquids

Guided Wave Radar Level Transmitter Calibration Procedure

Here, we introduce the relatively common debugging methods and means of guided wave radar level gauges. Users can determine the most appropriate method of use according to their actual situation. Finally proceed. Remember to be cautious when choosing a method, otherwise errors will easily occur.

  1. Via HART handheld programmer. However, the HART handheld programmer has its adjustment range, which is not suitable for all products. The measurement range is 4-20mA corresponding value.
  2. Through the handheld adjustment module. Its function is equivalent to an analysis and processing instrument. The programmer is composed of buttons and a liquid crystal display. The adjustment menu and parameter settings can be displayed.
  3. Through the debugging software. Guided wave radar level gauge can be debugged through software. The process is: mainly use HART software for debugging, and an instrument driver is needed. Among them, when using software for debugging, power up the radar instrument with 24VDC. At the same time, add a 250 ohm resistor to the front end of the HART adapter. If the integrated HART resistance power supply meter, the internal resistance is 250 ohms. There is no need to add an external resistor. At this time, the HART adapter can be connected in parallel with the 4–20mA line.
Guided Wave Radar Level Transmitter Calibration Procedure
Guided Wave Radar Level Transmitter Principle of Operation

Ultrasonic Level versus Guided Wave Radar Level

Ultrasonic level sensors are non-contact and provide a cost-effective choice for most straight-wall tank applications. Guided wave radar sensors are suitable for liquid and solid applications and operate independently of process conditions.

Ultrasonic level measurement technology

The ultrasonic liquid level sensor operates by transmitting the sound wave generated by the piezoelectric transducer to the surface of the processing material to be measured. The level sensor measures the length of time it takes for the reflected sound wave to return to the transducer. Successful measurement depends on the reflection of ultrasonic waves from the process material and movement back to the sensor in a straight line. Factors such as dust, heavy steam, water tank obstacles, surface turbulence, foam, and even surface angle will affect the return signal when using an ultrasonic level sensor. It is therefore necessary to consider how the operating conditions affect the sound waves.

  • Sound waves-Sound must travel through the medium (usually air). This makes the liquid level sensor unsuitable for use in vacuum applications where air molecules do not prevent sound waves from propagating.
  • Surface Condition-Foam and other debris collected on the surface of the liquid will absorb sound waves and prevent them from returning to the sensor.
  • Angle of incidence and angle of reflection-Sound waves must be sent and received in a straight line. And the reflective surface must be flat.
  • Operating temperature-Ultrasonic devices are usually plastic with a maximum operating temperature of 60°C. In addition, varying process temperatures may produce inaccurate level readings.
  • Working pressure-Ultrasonic equipment is not suitable for extreme pressure limits; the maximum working pressure should not exceed 30 psig.
  • Environmental conditions-Steam, condensed moisture and other contaminants will change the speed of sound through the air. And greatly affect the accuracy of the returned signal. Therefore, ultrasonic equipment should be installed in a predictable environment.

Guided wave radar (GWR) level measurement

Guided wave radar (GWR) is a method of contact level measurement. It uses a probe to guide high-frequency electromagnetic waves from the level gauge to the measured medium.GWR is based on the principle of Time Domain Reflectometry (TDR). Using TDR, low-energy electromagnetic pulses are guided along the probe. When the pulse reaches the surface of the measured medium, the pulse energy is reflected by the probe to the circuit. The circuit then calculates the liquid level based on the time difference between the transmitted pulse and the received reflected pulse. The sensor can output the analyzed level as a continuous measurement reading through the analog output. Alternatively, the value can be converted into a freely positionable switch output signal.

  • Unstable process conditions-changes in viscosity, density or acidity will not affect accuracy.
  • Stirring surface-boiling surfaces, dust, foam and steam will not affect the performance of the device. GWR can also be used with circulating fluids, propeller mixers and aeration tanks.
  • High temperature and high pressure-GWR performs well at temperatures up to 315°C and can withstand pressures up to 580 psig.
  • Fine powders and viscous liquids-GWR is used with vacuum tanks containing used cooking oil and tanks filled with paint, latex, animal fat, soybean oil, sawdust, carbon black, titanium tetrachloride, salt and grains.

Guided wave radar level transmitter price

Sino-Inst Guided wave radar level transmitter, made in China. Has a good product quality and price advantage. The price of our Guided wave radar level transmitter ranges from USD400-800. The specific product price needs to be determined according to the actual product parameters. So, if you need a quotation for Guided wave radar level transmitter, please contact our sales engineer in time. Provide your measurement requirements, and you can get the price of Guided wave radar level transmitter within 24 hours.

How does a radar level transmitter work?

Radar level transmitters use radar technology to perform non-contact continuous level measurement. The radar level indicator converts the level into an electrical signal. The level signal output can then be utilised by other instrumentation to monitor or control. Liquids and solids are commonly measured with this measuring technique. Like: Fly ash silo. Radar level sensors are divided into: Pulsed radar technology and frequency modulated continuous wave (FMCW) radar level sensors.

How do you calibrate a radar level transmitter?

Because the general testing distance of radar level transmitters is usually 2-10m or more than 10m. It is difficult to simulate the distance required for calibration in the laboratory. Therefore, radar level gauges mostly use online calibration. However, on-line routine calibration must use on-site process conditions. During the calibration period, on-site process equipment-storage tanks or reaction tanks must be shut down, which seriously affects on-site process production. At the same time, the on-site liquid level change is affected by the process conditions and the stabilization time is too long, so the online routine calibration time is usually longer.
Extended reading: Applications of Radar Corrosive Liquid Chemical Level Sensor

What is guided wave radar level transmitter?

Guided wave radar level transmitter is a radar level sensor based on the principle of time domain reflection (TDR).

Sino-Inst offers over 10 Guided Wave Radar level transmitters for level measurement. About 50% of these are Radar level meters, 40% is the tank level sensor.

A wide variety of Guided Wave radar level meters options are available to you, such as free samples, paid samples.

Sino-Inst is a globally recognized supplier and manufacturer of Guided Wave radar level measurement instrumentation, located in China.

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