How does guided wave radar work

Variations in level measurement can easily occur under these conditions, but the guided wave radar technology is unaffected by these changes. The device does not need to compensate for changes in density, dielectric, or conductivity in the fluid and this makes this top down measurement very robust. In many applications there is a need to measure both the level and the interface level.

An example is to detect unwanted oil on top of water, to see if your process has been compromised. This can be done using only one device. When the two different medias have different characteristics, the microwave reflects back when reaching both surfaces, providing a level and interface level measurement. With the Peak-in-Peak technology you can detect top layers down to 1 inch 25 mm. Level measurement using guided wave radar technology is based on the reflection of microwaves on surface media.

All media have a dielectric constant. The higher it is, the stronger the reflection of the microwaves will be. Vacuum gives no reflection at all and has a dielectric constant of 1. Oil is approximately 2 and water around A dielectric constant below 1. Levelflex works with high-frequency radar pulses which are emitted and guided along the probe.

As the pulse meets the medium surface, part of the emitted pulse is reflected due to a change of the dc value relative dielectric constant. The Time-of-Flight between pulse launching and receiving is measured and analyzed by the instrument and constitutes a direct measure for the distance between the process connection and the product surface.

Reliable measurement: Unaffected by medium surfaces and tank obstacles or baffles. Try searching by key words, order- or product code or serial number e. Guided radar level measurement Continuous level measurement in liquids and solids with guided wave radar sensors. The device transmits a microwave signal down the probe to the product surface, which reflects the signal back.

Then the transmitter can calculate that distance using the following formula:. So the radar measures the distance, but you want to know the level of the product, right? No worries. When you set up the transmitter, you include the minimum and maximum height of the application. Then the transmitter can calculate the level too! Good little gizmo! Some probes have specific characteristics which can limit the guided wave radar, like length and mounting restrictions.

And if you have high turbulence, then you need to anchor the base of the sensor. Guided wave radars generally use one of three types of probe — coaxial, twin element, and single element. Which will work best for you?

Usually vendors provide tables or charts to help you select the right probe for your application, but let me give you a quick overview. Coaxial probes cover a wide range of applications, including those with low dielectric constants in their products. For a long measurement range, the twin element probe is a good choice, and you can get a flexible or rigid one.

Level is among the most frequently measured process variables. The actual level readings are used for local indication, process automation and visualization in control systems. Additionally, level measurements are crucial for managing inventory and enforcing safety limits for overfill, leak detection or dry-run protection of pumps.

Other applications include automated ordering systems and communicating low limits to suppliers to streamline the logistic process. Guided wave radar GWR based on time-domain-reflectometry technology is one of the fastest growing methods for level measurement at chemical plants. Its popularity has risen sharply over the last twenty or so years. GWR now is handling applications that previously have used technologies such as capacitance, hydrostatics or ultrasonics.

In this article, we will look at why the acceptance of the technology is increasing, as well as the applications that can benefit most from this approach to level measurement.

Changes in temperature, pressure, density, dielectric constant or the measured material are just a few parameters that affect the choice of level measurement technology. Agitation, foaming, corrosive properties, dust and construction of the tank also influence the choice. Another factor can be the desire to use a single type of instrument for all level measurements.

Finally, the selection also depends upon unit price, lifecycle cost, ease of mounting, maintenance, accuracy, relevant certifications, and the ease of integrating the device into the control system. The growing cost of labor and the increasing demand for uninterrupted production are spurring interest in electronic measurement technologies. Their design, which involves no moving parts and features built-in diagnostics, results in reduced maintenance costs and higher reliability.

Electronic measurement technologies also provide significantly lower lifecycle costs than traditional mechanical and electromechanical level instruments. Besides GWR, electronic level measurement technologies available include bubbler, hydrostatic and differential-pressure instruments.

Products based upon these other technologies avoid some of the maintenance issues associated with mechanical technologies. However, they share a common disadvantage: sensitivity to changes in the density of the measured product. Capacitance level measurement, in some applications, may become sensitive to changes in dielectric constant of the measured product.

Ultrasonic level measurement is an excellent way to measure level — provided the path of the ultrasonic signal is clear of obstacles and foams, dust or heavy vapors, and the application falls within its limited operating pressure and temperature ranges. These limitations demonstrate the need for a reliable and maintenance-free level measurement technology that can cope with a wide range of pressures and temperatures while being insensitive to changes in density or dielectric constant.

It would be ideal if the measurement device had maximum immunity to heavy vapors, dust or foaming, and the turbulent surface of the measured product.

Moreover, the recent drop in prices of radar devices makes them competitive with the more economical ultrasonic level instruments. Their benefits in performance and application range justify their higher price. They send electromagnetic pulses toward the measured product and use the reflected signal to calculate the level in the tank.

NCR relies on a sophisticated antenna to send the measured signal and retrieve it after reflection. With GWR, the measured signal travels along a waveguide that can be made of a stiff metallic rod, flexible wire or a coaxial construction.