Level gauges. Application features

Abstract

This paper considers various aspects of application of the most common types of level gauges – magnetostrictive, servo-driven, radar and reflex. Much attention is paid to accuracy of level gauges, expressed in error and uncertainty, including those referred to the legally regulated measuring instruments. Due to the fact that the most of the level gauges are installed on tanks, the requirements for them, given in the standards, and possible ways to improve the accuracy of level gauges installed on tanks have been analyzed. Methods of verification and calibration of level gauges are considered, including both verification on standard units using water, and carried out by the simulation method.
 The requirements for the metrological control of level gauges with moving parts are stated. It is shown that for verification of such level gauges, it is necessary to carry out measurements when the water moves both up and down. However, there is no need to take measurements, as in determining the variation, at the same points when the water moves up and when the water moves down.
 Some known caution is needed when using the results of the verification of level gauges by the simulation method. Especially big differences in the results of verification on the standard unit with water and the simulation method are observed for magnetostrictive level gauges.
 This difference is due to the fact that in these level gauges, the float slides along the pipe with a certain friction, and in the simulation method, the float moves by hand and its movement does not depend on friction.