User`s manual

Section 5: Configure Menu, Part III - Calibration Coefficients
58
• Chelsea PAR sensor
Calibration constant
= 10
9
/ 0.01 (for units of microEinsteins/sec–m
2
) or
= 10
9
/ 0.04234 (for units of quanta/sec–m
2
)
M = 1.0 / (log e * A1 * 1000) = 1.0 / (0.43429448 * A1 * 1000)
B = - M * log e * A0 = - M * 0.43429448 * A0
where A0 and A1 are constants from Chelsea calibration sheet with an
equation of form: PAR = A0 + (A1 * mV)
Multiplier can be used to scale output, and is typically set to 1.0.
Note: SEASAVE can process data for an instrument interfacing with up to two
PAR/irradiance sensors when using the New Style configuration.
Biospherical Surface PAR Sensor
A surface PAR sensor is selected by clicking Surface PAR voltage added in
the Configure dialog box. Enter conversion factor and ratio multiplier.
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 when using the New Style or Old
Style configuration.
Suspended Sediment Calibration Coefficients (New Style
configuration only)
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.
Notes:
• Selection of Par / Irradiance,
Biospherical / Licor as the voltage
sensor is also applicable to the
Chelsea PAR sensor.
• For complete description of
calculation of surface PAR
calibration coefficients,
see Application Note 11S
(SBE 11plus Deck Unit) or 47
(SBE 33 or 36 Deck Unit).