User`s manual

Section 4: Configure Inputs, Part II - Calibration Coefficients
47
pH Calibration Coefficients
Enter the slope and offset from the calibration sheet:
pH = 7 + (Vout – offset) / (°K * 1.98416e-4 * slope)
where
°K = temperature in degrees Kelvin
Pressure/FGP (voltage output) Calibration Coefficients
Enter scale factor and offset.
output [Kpa] = (volts * scale factor) + offset
where:
scale factor = 100 * pressure sensor range [bar] / voltage range [volts]
Note: SEASAVE can process data for an instrument interfacing with
up to eight pressure/fgp sensors.
Suspended Sediment Calibration Coefficients
The Sequoia LISST-25 sensor requires two channels – one for scattering
output and the other for transmission output. Make sure to select both when
configuring the instrument.
For the scattering channel, enter Total volume concentration constant (Cal),
Sauter mean diameter calibration (α), Clean H
2
O scattering output (V
S0
), and
Clean H
2
O transmission output (V
T0
) from the calibration sheet. For the
transmission channel, no additional coefficients are required; they are all
defined for the scattering channel.
Optical transmission = τ = V
T
/ V
T0
Beam C = - ln (τ) / 0.025 [1 / meters]
Total Volume Concentration = TV = Cal * [ ( V
S
/ τ ) - V
S0
] [μliters / liter]
Sauter Mean Diameter = SMD = α * [ TV / ( - ln (τ ) ] [microns]
where
V
T
= transmission channel voltage output
V
S
= scattering channel voltage output
The calibration coefficients supplied by Sequoia are based on water containing
spherical particles. Perform calibrations using seawater with particle shapes
that are similar to what is expected in situ.
Notes:
• See Application Notes 18-1, 18-2,
and 18-4 for complete description
of calculation of pH calibration
coefficients.
• SEASOFT-DOS < version 4.008
ignored temperature compensation
of a pH electrode. The relationship
between the two methods is:
pH = pH old + (7 – 2087/°K)
For older sensors, run pHfit version
2.0 (in SEASOFT-DOS) using
Vout, pH, and temperature values
from the original calibration sheet
to compute the new values for
offset and slope.