Campbell Scientific AL200 ALERT2 Encoder, Modulator, and Sensor Interface User Manual

Page 42

Appendix H. Calculating Multipliers and Offsets

Now, we can calculate pressure based on the reading we get from the sensor.

For example, you measure the sensor’s output as 2543.210 mV. Pressure

would be determined by:

Pressure = (0.0060 • 2543.210) + (–0.074) = 15.263 psi

To determine water depth, simply multiply the pressure value by the

appropriate conversion factor.

For fresh water this is:

1 psi = 2.308 ft.

For salt water this is:

1 psi = 2.250 ft.

For the above example (assuming fresh water):

Depth of Water = Pressure • 2.308

Depth of Water = 15.263 • 2.308 = 35.226 ft.

These calculations can easily be performed using many spreadsheet programs

by plotting the sensor’s measurement range versus the sensor’s output range.

The equation of the trendline contains the multiplier and offset.

H-2