- By means of directly measuring submersible pressure probesThe pressure transducer is usually fitted with a special cable with a small "hollow" piezometer which indicates the atmospheric pressure value to the probe and thus by means of the differential pressure the value is usually given in the form of 4-20ma.
It is a very effective and simple system but has two main problems One is the price of the cable with piezometer tube, which can be prohibitively expensive at great depths, and the other is the interference that can be caused by modern pumping equipment control systems such as variable speed drives, which can introduce "electrical noise" into the system and cause the reflected values to fluctuate and become unusable once the system is running.
By means of indirect measurement controllers: The SONDELEVEL system is based on the indirect measurement system using compressed air described above and, although it requires a piezometer tube and a compressed air compressor, it is a more economical system and much more resistant (it is not affected) to "electrical noise" than the previous system. It also shows the depth value on the display and by means of two simple potentiometers it allows us to control a relay and its hysteresis to control the pumping equipment. It also includes an analogue output with the depth of the well, which can be exported (for example) to an inverter to avoid overexploitation of a borehole (as an example).
In conclusion, we can say that indirect measurement systems, whether point or continuous, based on compressed air, are not only simple to implement and operate, but also very resistant to the effects of "electrical noise", which can render expensive differential pressure transducer installations unusable (as is often the case).