Water Level Monitoring
Submersible Pressure Transducers
Submersible pressure transducers (SPT) are submerged at a fixed depth below the water surface and measure equivalent hydrostatic pressure of the water head above the sensor diaphragm for the calculation of the total liquid depth. Vented pressure sensors, which use a vented cable to connect the base of the pressure transducer to atmospheric pressure, compensate for barometric pressure changes at the surface.
Variances in accuracy of measurement depend on the model of pressure sensor used, the accuracy of some sensors is reduced by temperature variation, nonlinearity and hysteresis, as well as long-term drift. The potential for sensor fouling should be a consideration before installation of SPT.
SPTs can be used in a wide range of applications, including for both surface and groundwater as well as tanks.
A shaft encoder is an electro-mechanical device which converts the position of a shaft to an electrical signal. The rotational shaft utilizes a float and counter-weight attached to a line or tape placed around a pulley, as the water level changes, the float moves up and down and rotates the shaft, which records a change in water level.
Shaft encoders can be use in some surface water applications and for pan evaporation monitoring.
Ultrasonic water level instruments use sound waves in frequency range ~20-200 kHz to
determine fluid level. A transducer directs bursts sound waves down onto the surface of
the water which then reflects an echo of these waves back to the transducer. The transducer performs calculations to convert the distance of wave travel into a measure of height, and therefore distance to water surface.
The accuracy of Ultrasonic sensors can be affected by condensation on the transducer
and very high concentrations of fine sediment in suspension, which can scatter and absorb
the sonic pulse.
Ultrasonic sensors can be use in some surface water applications and for tank monitoring.