What are the key advantages a radar-based level transmitter offers over traditional level measurement technologies (i.e. differential pressure, RF capacitance, magnetostrictive, etc.)?
Guided-wave radar overcomes a number of weaknesses in many of the older technologies. Being immune to changes in specific gravity, GWR outperforms DP cells and displacer transmitters.
In addition, the fact that GWR has no moving parts, it eliminates the issue of mechanical parts needing maintenance or losing their tolerance.
The biggest concerns with RF capacitance applications are:
- the need to move levels to calibrate the device; and
- changing dielectric constants.
GWR does not require level movement and no field calibration is necessary.
Secondly, since GWR is only looking for an impedance change between the air and liquid level, changing dielectric constants do not affect GWR.
As long as the dielectric constant of the medium is high enough to be detected as a level, a change in dielectric does not affect performance.
In other words, the position, in time, of the reflection does not change with changing dielectric constant — only the amplitude of the signal changes.
Another weakness of RF capacitance is that significant measurement error can occur if a conductive medium coats and builds up on the probe.
A single-rod GWR probe can operate effectively even with coating and build up, although some error will develop based on the extent of the coating.
One major advantage GWR offers over Magnetostrictive technology is that it has no moving parts. This lends itself to applications in the food/beverage and biotech industries that require a sanitary finish.
Author - Bob Botwinski