Enhance water-sqrt rate subtype

"Baseline rate krunching using the "water" subtype does not work as needed for the water customers. When this subtype calculation is needed, we have had to modify the cnvrat function in genrat.cpp to correct the formula. Since we can no longer do that in Enterprise SCADA, we need the formula to be corrected in baseline.

The baseline formula to calculate the flow rate is to multiply the water constant by the square root of the converted raw value:

newrat = water_cnstnt * sqrt(rawrat), where rawrat is the converted raw value.

However, the converted raw value actually needs to be normalized between 0 and 1 before taking the square root and then multiply it by the span before multiplying it by the water constant. The following external link describes this in detail: https://www.crossco.com/resources/technical/square-root-scaling-for-differential-pressure-flow-meters/

So, the correct formula should be:

rawrat = ( egumax – egumin ) * sqrt( (rawrat – egumin)/(egumax –egumin) ) + egumin (where rawrat is the converted raw value)

newrat = water_cnstnt * rawrat

For example, assume a point with water_constant 1, min egu = 0, max egu = 20, min raw = 0 and max raw = 10000. Using a linear subtype gives a currate of 9 when the register raw value is 4500. The current baseline water-sqrt subtype gives a currate of 3 (square root of 9). But the correct value with the water_sqrt subtype should be 13.42."

SE-WWW regularily updated the baseline code for this calculation and are now not able to.