Load Cells for Gravitational Level Measurement

The views and opinions expressed in this article about load cells and gravitational level measurement are entirely those of the contributor and are in no way a reflection or indication of Eilersen.com.

There are many occurances in light, medium and heavy industry where the level measurement must be recorded and utilizing a load cell to measure the gravitational level is a suitable solution. It is common to find a strain gauge type load cell fitted against each leg of the tank or silo to calculate the level however with susceptibility to shocks, tremors and overloads a better load cell to use would be a non-contact capacitive digital load cell.

To take the Level measurement pipes connected to the tank should have the highest possible flexibility to vertical movements and the stiffness of the pipes may to a certain degree be calibrated out by changing the slope of the signal voltage. In installations where all the legs of the tank are supported by load cells, horizontal forces will not cause weighing errors as they will only shift the load from one load cell to another, but the sum of the load cell outputs will remain constant - hence even if the liquid is not settled a true and accurate measurement reading can be taken by the load cells. In installations where the tank is completely supported by load cells and the flexibility of the pipes connected to the tank is high, the weighing system may simply be calibrated electronically by the supplier.

It is not always suitable, for whatever reason, to install a supporting load cell to each leg of a tank. In such installations where not all the legs of the tank are supported by load cells the pipes should also have a high flexibility to horizontal movements. Otherwise the pipes, especially if they are connected to the top of the tank, will be able to shift the load to or from the tank leg with the load cell and thus cause weighing errors.

On account of the new, continuous and contact-free technology digital capacitive load cells can be used in many level monitoring applications within medical technology, chemical and pharmaceutical industries, also biotechnology as well as food and beverage. The non-invasive design, with no contact between the sensor and the fluid, eliminates all media compatibility and sterility issues. For level measurement for a tank or silo with three legs it is possible to use one load cell and achieve an accuracy of about 1,5%.