Measuring the water flowing through the vine is equivalent to asking the plant if it’s thirsty. What we want to know is how much water the plant is actually using compared to how much it would theoretically use in a given climate and environment. To understand the impact, we look at four climactic parameters -- sun, temperature, relative humidity and wind -- and compute how much the plant would transpire given an unlimited supply of water in the ground. We compare those numbers to the actual transpiration measured by the sap sensors. Comparing the two allows us to compute the water deficit across time. We show that data to the customer, and then work with them to decide when to water next and how much
https://www.greenbiz.com/blog/2013/06/19/fruition-sciences-finer-wine-through-data