# Analog 2 Point Scaling

It may be useful in comprehending the process of establishing the scaling factors, to visualize a graph that relates the water level in a tank to the input from a 4-20ma transducer. To establish the relationship on such a graph, it is necessary to define two separate points, or coordinate pairs ideally at two widely separated points on the graph. For such a linear relationship any point on the “reading” may be calculated from the formula:

Y = Mx + b

Where M is the gain and b is the zero crossing point or Input (ma -> offset). The gain may be calculated from:

M = (y2-y1)/(x2-x1)

Where x1, y1 is on coordinate pair on the graph and x2, y2 is the other.

Example:

recorded values of Y1 and Y2.