User`s manual

Section 4: Configure Inputs, Part II - Calibration Coefficients
43
Methane Sensor Calibration Coefficients
The Capsum METS sensor requires two channels – one for the methane
concentration and the other for the temperature measured by the sensor. Make
sure to select both when configuring the instrument.
For the concentration channel, enter D, A0, A1, B0, B1, and B2.
Methane concentration
= exp {D ln [(B0 + B1 exp ) * ( – )]} [μmol / l]
Where
Vt = Capsum METS temperature voltage
Vm = Capsum METS methane concentration voltage
For the temperature channel, enter T1 and T2.
Gas temperature = (Vt * T1) + T2 [°C]
OBS/Nephelometer Calibration Coefficients
In general, turbidity sensors are calibrated to a standard (formazin). However,
particle size, shape, refraction, etc. in seawater varies. These variations affect
the results unless field calibrations are performed on typical water samples.
• Downing & Associates [D&A] OBS-3 Backscatterance
Enter gain and offset.
output = (volts * gain) + offset
where
gain = range/5; see calibration sheet for range
• Downing & Associates [D & A] OBS-3+
Enter A0, A1, and A2.
output = A1 + (A1 * V) + (A2 * V
2
)
where
V = voltage from sensor (milliVolts)
A0, A1, and A2 = calibration coefficients from D & A calibration sheet
Note: SEASAVE can process data for an instrument interfacing with up to
two OBS-3+ sensors.
• Chelsea
Enter clear water value and scale factor.
turbidity [F.T.U.] = (10.0
V
– C) / scale factor
where
V = voltage from sensor
See calibration sheet for C (clear water value) and scale factor
• Dr. Haardt Turbidity
Enter A0, A1, B0, and B1. Select the gain range switch:
¾ Output Voltage Level if the instrument indicates gain by output
voltage level (< 2.5 volts is low gain, > 2.5 volts is high gain)
Low gain: value = A0 + (A1 * V)
High gain: value = B0 + (B1 * V)
¾ Modulo Bit if the instrument has control lines custom-wired to bits in
the SBE 9plus modulo word
Bit not set: value = A0 + (A1 * V)
Bit set: value = B0 + (B1 * V)
¾ None if the instrument does not change gain
value = A0 + (A1 * V)
where
V = voltage from sensor
Note:
See Application Note 16 for
complete description of OBS-3
calibration coefficients.
-Vt
B2
1
Vm
1
A0 – A1 * Vt
Note:
• See Application Note 81 for
complete description of calculation
of OBS-3+ calibration coefficients.
• You can interface to two OBS-3+
sensors, or to both the 1X and 4X
ranges on one OBS-3+ sensor,
providing two channels of
OBS-3+ data.