Example 1: corr_pH - Simple temperature correction of pH

Consider an RBRconcerto C.T.D.pH logger. Without temperature correction, the pH output from Channel-4 would be a simple linear function of the raw data:

where R is the normalized voltage ratio from Channel-4 monitoring the pH sensor,c0,c1 are the core coefficients of the linear equation, andpHraw is the uncorrected output in pH units.

The parameter pH is well known to have a dependence on temperature, so a more accurate value is obtained if the compensated version of the equation is used. This is typically expressed in a form such as:

Casting this into the form used by the logger, corr_ph, is simple:

where

• pHraw is c0 + c1 * R as before, now an intermediate variable in the equation,
•  x0 corresponds directly in value to the constant 'Kph',
•  x1 is the calibration pH 'pHcal', generally 7.0,
•  x2 is the calibration temperature 'Tcal' in °C,

•  n0 is the index of the temperature channel (2 in this example),
  value(n0) is the final output value of the temperature channel in °C,

• pHcorr is the corrected output in pH units.

Note that this equation is for the output from Channel-4, so the source of the primary raw data R is implicitly Channel-4: there is no 'n' index to specify where the raw data originates.

Example commands:

( Confirm the channel type )

( Set the core coefficients ) 

( Set the cross-channel correction coefficients ) 

( Request confirmation of everything )