Scaling A Linear Sensor

To solve for these values, solve the equation: y = mx + b Where the y-axis represents the sensor reading in any unit, and the x-axis represents the corresponding voltage input to the Data Dolphin. If we assume that we are converting a 4-20ma output to voltage via the use of a 100Ohm shunt resistor, then the total voltage range on the input will be 0.4 – 2 Vdc. In the example of the PH Probe,

12 PH

0 PH 0.4 V

m=slope=changein y/change in x = 12/1.6 = 7.5 and then: 12 = (7.5)(2) + b, and solving for b = -3

2V