Compare between Guided wave and noncontracting radar gauge

Non-contact radar is radar that is based on microwave technology that sends the microwave signals through the air and not a medium. On the other hand, Guided Wave Radar instruments uses wave guide “probes” to guide radio waves into a process fluid. Both of these techniques are used to measure the surface level of fluids in a container. Below are some of the differences between the two radar level measurement techniques.

1. Measurement principle:

Measurement principle is through microwave pulses that travel through air into the fluid to get the surface level measurements.

2. Non-contact measurement type:

The measurement type is non-contact which means the fluid is not in contact with the sensors.

3. Measurement accuracy:

The air space will determine the measurement accuracy and this makes it difficult to obtain measurements in extremely difficult applications.

4. Top mounted:

The sensors are mounted at the top of the cylinder.

5. It is cost effective:

It is moderately priced but may require additional expenses in terms of maintenance.

6. Acceptable performance:

The performance of this radar is based on the strength of reflection and the surface conditions. If the reflection is weak, then the measurement may be impaired. Likewise, if the reflection is strong, then more accurate measurements may be achieved.

7. Easy to set up:

It is easy to install thanks to the quick connection and disconnection that does not require initial set-up and continuous maintenance.

8. It can easily track fast moving level changes:

The non-contact radar technology is not based on contact of the fluid and this means that in case there is any change in the level of the fluid, the measurement will easily be tracked.

9. The level measurement is not actual but inferred:

Unlike when using GWR, the measurement of the fluid level may not be accurate but inferred. This means that multiple measurements need to be taken before an accurate figure can be determined.

10. Low noise levels:

The Non-contact radar records extremely lower noise levels as compared to the GWR when in operation due to the non-contact type technology.

1. Measurement principle:

The measurement principle is based on high-frequency radar impulses that are transferred through a probe down onto the interface of the two liquids in the container.

2. Contact measurement:

The measurement technique for GWR is through contact which means the probe must be in contact with the fluid in order for the surface level measurement to be taken.

3. Extreme conditions:

The measurement accuracy of this technique is not affected by extreme temperatures and pressure since the fluid interface accuracy is determined by the dielectric constant of the fluid.

4. Top mounting:

Top mounted but this is affected if there is a mixer or an obstacle in the tank which will have an impact on the reading or measurement of the surface level.

5. Competitive cost:

The GWR is offered at an extremely affordable cost and does not also require intense maintenance. This means that the cost of operation is relatively lower than other surface level measurement techniques.

6. High performance:

The GWR has a higher performance and is independent of the process conditions of the fluid and the container.

7. Direct measurement:

The GWR provides the exact measurements of the fluid level and the interface of the two fluids in a container. There are no estimates in the measurements of the surface level.

8. Higher noise levels in operation:

GWR records higher noise levels when working because of the physical contact with the fluid during operations.

9. Low sensitivity to foam and build up:

The reading and measurement might be affected by foam of the liquid. In light foam conditions, the signal may ignore the foam and record the exact fluid level. This may not be true with heavy foam.


10. No moving parts:

It has flexible measurement options with no moving parts


11. Susceptible to corrosion:

Since the fluid is in contact with the probe, the probe may be corroded especially if the fluid is corrosive and this may affect the measurement.

Advantage :-

  • Non-contacting radar provides a top-down, direct measurement as it measures the distance to the surface.
  • It can be used with liquids, sludges, slurries and solid.
  • No impact on accuracy if change pressure, Temperaturedielectricconductivity and density.
  • Radar devices have no moving parts so maintenance is minimal.
  • No calibration required GMR required only simple configuration.
  • It is a top-down, direct measurement as it measures the distance to the surface.

Disadvantage / Limitations

For non-contacting radar, good installation is the key to success. The gauge needs a clear view of the surface with a smooth, unobstructed, unrestricted mounting nozzle. Obstructions in the tank, such as pipes, strengthening bars, and agitators can cause false echoes, but most transmitters have sophisticated software algorithms to allow masking or ignoring of these echoes.

Non-contacting radar gauges can handle agitation, but their success will depend on a combination of the fluid properties and the amount of turbulence. Dielectric constant (DK) of the medium and the surface conditions will impact the measurement. The measurement may be influenced by the presence of foam. Energy tends to not be reflected by light and airy foam while a dense and heavy foam typically reflects the energy.

Advantage :-

  • Guided wave radar (GWR) provides an accurate and reliable.
  • Continuous level measurement.
  • GWR is easy to install and enables simple replacement of older technologies
  • GWR can be used with liquids, sludges, slurries, and some solids.
  • Changes in pressure, temperature Gravity and vapor pressure have no impact on the accuracy of radar measurements.
  • radar devices have no moving parts so maintenance is minimal.
  • No calibration required GMR required only simple configuration.

Disadvantage / Limitations

  • High cost as compared with other instruments.
  • While guided wave radar works in many conditions, some precautions need to be taken with respect to probe choice. Several probe styles are available and the application, length, and mounting restrictions influence the choice. Unless a coax-style probe is used, probes should not be in direct contact with a metallic object, as that will impact the signal. If the application tends to be sticky or coat, then only single lead probes should be used. Some advanced GWRs on the market have advanced diagnostics, with the ability to detect build-up on the probe. Chambers with a diameter less than 3 in. (75 mm) may cause problems with build-up and may make it difficult to avoid contact between chamber wall and probe.