Servo Gauge Tank Level Measurement

Tank gauging system is based on the principle of displacement measurement. A small displacer is accurately positioned in the liquid medium using a servo motor. The displacer is suspended on a measuring wire that is wound onto a finely grooved drum housing within the instrument. The drum is driven...
Continue reading »

Radiation type level measurement

Certain types of nuclear radiation easily penetrates the walls of industrial vessels, but is attenuated by traveling through the bulk of material stored within those vessels. By placing a radioactive source on one side of the vessel and measuring the radiation making it through to the other...
Continue reading »

Capacitive level measurement

Capacitive level instruments measure electrical capacitance of a conductive rod inserted vertically into a process vessel. As process level increases, capacitance increases between the rod and the vessel walls, causing the instrument to output a greater signal. The basic principle behind capacitive level instruments is the capacitance...
Continue reading »

Magnetostrictive level measurement

A variation on the theme of echo-based level instruments, where the level of some process material in a vessel is measured by timing the travel of a wave between the instrument and the material interface, is one applied to float-type instruments: magnetostriction. In a magnetostrictive level instrument,...
Continue reading »

Ultrasonic level measurement

Ultrasonic level instruments measure the distance from the transmitter (located at some high point) to the surface of a process material located farther below using reflected sound waves. The frequency of these waves extend beyond the range of human hearing, which is why they are called ultrasonic. The...
Continue reading »

Bubbler systems

An interesting variation on this theme of direct hydrostatic pressure measurement is the use of a purge gas to measure hydrostatic pressure in a liquid-containing vessel. This eliminates the need for direct contact of the process liquid against the pressure-sensing element, which can be advantageous if the process...
Continue reading »

Conductive level switch

Perhaps the simplest (and oldest) form of electrical level detection is where a set of metal electrodes contacts the process material to form a complete electrical circuit, actuating a relay. This type of switch, of course, only works with granular solids and liquids that are electrically conductive...
Continue reading »