What is the best way to measure the level of diesel fuel in a very shallow tank, for example, one that is only 20 centimetres (about 8 inches) deep?
Measuring liquid level in very shallow tanks presents a challenge, as standard submersible sensors may have a minimum range that is too high, leading to poor measurement resolution. For a tank just 20 cm deep, it is crucial to select a sensor with a very low measurement range.
A suitable solution is a pressure transmitter with a variable capacitance flush ceramic diaphragm. These sensors are available with a low pressure range of 0 to 40 millibar (mbar), which corresponds to 0 to 40 centimetres of water column (cmH2O).
Featured shallow depth liquid level sensor products
LMK 858 Plastic Submersible Liquid Level Sensor with Removable Cable - Chemical resistant liquid level sensor with detachable signal cable for measuring quantity of aggressive media such acids and alkalis and sludge in tanks located outside of factory buildings.
LMK809 Plastic Submersible Low Level Transmitter - IP68 low range pressure transmitter for measuring the level of highly contaminated and agressive liquid media with a body made from PP-HT or PVDF.
To determine the pressure range needed, we can calculate the pressure exerted by the diesel fuel. The specific gravity (SG) of diesel is approximately 0.832. Therefore, a 20 cm depth of diesel exerts a pressure equivalent to: 20 cm x 0.832 (SG) = 16.64 cmH2O.
This pressure (approx. 16.6 mbar) fits comfortably within the 0-40 mbar range, utilizing over 40% of its measurement span. This ensures a much better signal resolution compared to a sensor with a higher standard range, such as 100 mbar (1 mH2O).
Furthermore, the flush diaphragm design is particularly advantageous for diesel fuel, which can be viscous. A flush surface prevents the accumulation of residue that could otherwise clog a sensor with a recessed diaphragm, ensuring accurate and reliable readings over the long term.
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