Example 3: corr_pres2 - temperature correction of pressure
Returning to the example of an RBRconcerto³ C.T.D.pH logger, the pressure reading from Channel-3, without correction for the effect of temperature on the sensor, is given by a cubic polynomial:
where R is the normalized voltage ratio from Channel-3 monitoring pressure, c0...c3 are the core coefficients of the cubic polynomial equation, and Praw is the uncorrected pressure output, reported in dbar for RBR instruments.
The equation which accounts for residual temperature sensitivity of the pressure sensor is:
Casting this into the form used by the logger would yield:
where
Praw is the cubic polynomial in R, as before,
x0 is the calibration pressure 'Pcal' in dbar,
x1, x2, x3, x4 correspond directly to the constants "Kp1" through "Kp4",
x5 is the calibration temperature "Tcal" in °C,
n0 is the index of the temperature channel "T",
value(n0) is the final output value of the temperature channel in °C,
Pcorr is the corrected output in dbar.
Examples
>> calibration 3 type
<< calibration 3 type = pres19Confirm the channel type.
>> calibration 3 datetime = 20171201000000, c0 = 0.2346, c1 = 120.9873, c2 = 2. 7356, c3 = 0.7Set the core coefficients.
>> calibration 3 datetime = 20171201000000, x0 = 9.983, x1 = 0.2003, x2 = 0.2943, x3 = 0.0721, x4 = 0.1049, x5 = 21.29Set the cross-channel correction coefficients.
>> calibration 3
<< calibration 3 type = pres19, datetime = 20171201000000, c0 = 0.2346, c1 = 120.9873, c2 = 2. 7356, c3 = 0.7, x0 = 9.983, x1 = 0.2003, x2 = 0.2943, x3 = 0.0721, x4 = 0.1049, x5 = 21.29, n0 = 2Request confirmation of all calibration coefficients.