There are four basic types of servo gauge:
First, is the low-accuracy pulse radar units, such as those made by Endress+Hauser, Siemens/Milltronics, and Ohmart/Vega. Now these are only “low accuracy” when compared to units designed for tank farm gauging. These are excellent general purpose radar units, but they are limited in use to materials with dielectric coefficients greater than about 8 or so. It generally rules them out for low viscosity hydrocarbons.
Second is the various radar-by-wire designs, such as Alliant(Bindicator-Celtek) and Magnetrol, etc. These are mostly used for solids, but could be used in hydrocarbons. They are also relatively
inexpensive.
Next are the FMCW units, these are moderately high accuracy, and can be used in gauging fluids with a dielectric of 3-5 or so. The compromises made in the designs of these units in order to make them look through small (4″<100 mm> to 6″ <150 mm>) vessel ports reduces the accuracy and the ability of these units to see lower dielectric constants. These are designed as
process servo gauges, not tank farm designs.
The highest level of accuracy are the units designed specifically for Tank Farm Gauging, they were designed to compete specifically with servo gauges and with hydrostatic level gauge and are designed to be used specifically for tank farms. These servo gauges consistently outperform their competition but are very expensive.
This article comes from control edit released