User`s manual

Section 4: Configure Inputs, Part II - Calibration Coefficients
49
User Polynomial (for user-defined sensor) Calibration
Coefficients
The user polynomial allows you to define an equation to relate the sensor
output voltage to calculated engineering units, if your sensor is not pre-defined
in Sea-Bird software.
Enter a0, a1, a2, and a3.
Value = a0 + (a1 * V) + (a2 * V
2
) + (a3 * V
3
)
where:
V = voltage from sensor
a0, a1, a2, and a3 = user-defined sensor polynomial coefficients
If desired, enter the sensor name. This name will appear in the data file header.
Note: SEASAVE can process data for an instrument interfacing with up to
three sensors defined with user polynomials.
Wet Labs ECO-FL-NTU Example
For the turbidity channel, NTU = (Vsample – Vblank) * scale factor
Set this equal to user polynomial equation and calculate a0, a1, a2, and a3.
(Vsample – Vblank) * scale factor = a0 + (a1 * V) + (a2 * V
2
) + (a3 * V
3
)
Expanding left side of equation and using consistent notation (Vsample = V):
scale factor * V – scale factor * Vblank = a0 + (a1 * V) + (a2 * V
2
) + (a3 * V
3
)
Left side of equation has no V
2
or V
3
terms, so a2 and a3 are 0; rearranging:
(– scale factor * Vblank) + (scale factor * V) = a0 + (a1 * V)
a0 = – scale factor * Vblank a1 = scale factor a2 = a3 = 0
Zaps Calibration Coefficients
Enter M and B from calibration sheet.
z = (M * volts) + B [nmoles]