Example 4: corr_cond - Conductivity corrections

Continuing with the RBRconcerto C.T.D.pH logger, the conductivity reading from Channel-1 without corrections is given by a simple linear function:

where R is the normalized voltage ratio from Channel-1 monitoring conductivity, c0,c1 are the core coefficients of the linear equation, and Craw is the uncorrected conductivity output, reported in mS/cm for RBR marine instruments.

The equation which corrects the output for the effects of both temperature and pressure on the conductivity cell is:

Casting the equation into the style used by the logger would give:

where

• Craw is the uncorrected conductivity, c0  +  c1*R,
• x0 , x1 , x2 correspond directly to the constants 'Kc1', 'Kc2' and 'Kc3',
• x3  is the calibration temperature 'Tcal' in °C,
• x4  is the calibration pressure 'Pcal' in dbar,
• n0  is the index of the temperature channel, in this example 2,
  value( n0 ) is the final output value of the temperature channel in °C,
• n1  is the index of the pressure channel, in this example 3,
  value( n1 ) is the final output value of the pressure channel in dbar,
• Ccorr is the corrected output in mS/cm. 

It is quite common to have a logger monitoring conductivity and temperature without a pressure channel, typically deployed at a known, constant depth. In this case, n1 would be set to "value", and so value(n1) would be substituted by a default value (see the "settings pressure" command).

Example commands:

( Confirm the channel type )

( Set the core coefficients )

( Set the cross-channel correction coefficients )

( Request confirmation of everything )