We needed to weigh thousands of gallons of water. We needed to set a volume by precise weight for our experiments. We could have just filled the tank with a precise amount of water, but the problem is in the precision. When measuring out thousands of gallons at a time, a little is lost or gained. It is never really accurate. Also, evaporation by the end of the day could account for enough weight to affect our experiments. We decided to use a load cell cable system under the huge tank to keep track of the weight of the water as we did our experiments.
A load cell system can weigh anything from a person to trucks and more. There are all kinds of types of load cells to put under objects to monitor their weight. We needed real time weight measurements as we did the experiments. Our data needed to be precise with less than a pound of fluctuation with the total weight of the water. Just splashing some out as we moved the test objects could easily lose us more than a pound in weight of water. Our load cell array was capable of measuring precisely the weight of the water in the tank if it was twice the size.
Think of it as a giant bathroom scale. The load cells in your digital bathroom scale measure your weight electronically and display it on a screen. We had pretty much the same thing. It was only a lot larger. It measured 240,000 pounds of water which is 30,000 gallons. The weight of the tank was the tare weight. That is, the load cell array disregards the weight of the tank on the cells and only weighs any additional weight put on them. We would take a measurement for every experiment sometimes adding or extracting as little as a cup of water.