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E-Zine August 2011Still another proprietary technique can be used for liquids with dielectric constants as low as 1.05. The radar beam passes through the vapor space and liquid before being reflected back to the sensor by bottom of the vessel. Information from the reflected signal is then processed to infer the liquid level in the vessel. Noting that the radar signal travels to and from the material, degradation of the signal strength between the sensors and the material can cause radar level measurement systems to fail to operate. Degradation can occur at the antenna, in transit to/from the material, and at the surface of the material. Dirt or other coatings on the radar antenna can cause the received signal to be weak. When accumulations over time are normal for the process, routine maintenance may be required to keep the transmitter/receiver operating. In many applications, the sensor may be shielded from the process and/or continuously purged with gas to keep it in operation. Careful analysis of the sensor design should be performed. Some designs inherently tend to keep the sensor from accumulating material while others tend to inherently accumulate material. Excerpted from The Consumer Guide to Non-Contact Level Gauges ISSN 1538-5280 |
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