All other equations currently implemented in the logger involve cross-channel dependencies, and so are intrinsically more complicated. A cross-channel dependency exists if the output of a channel depends on raw data from more than one channel in the logger. Typically, there is a primary raw input from the channel in question, with one or more secondary inputs from other channels, but there are other variations.
The equation type used for such a channel has knowledge of these dependencies built into it, but needs to be told which channel(s) in this particular logger are to be used. For a given channel type, just as the values of the usual coefficients in the c group vary from one logger to another, so will the values of the coefficients in the cross-compensation group x.
In many cases it is both useful and feasible for a channel to be recalibrated by end users, and typically it is the c group coefficients which will need to be changed. The cross-compensation coefficients in the x group often do not vary significantly over time, and may be much harder to determine. Although it is possible for OEM users to modify the values, it is not recommended as routine practice; one reason for using a different name for these coefficients is to act as a warning cue against accidental modification.
The indices of the secondary input channels in the n group will also differ between loggers. For example, a temperature channel required for compensation may be Channel-1 in one logger, but Channel-3 in another. The index values are configured at the factory and can not be changed by users, but their values can be read.
There is one special case when the value of an n index may be the text field "value". Again, this can be set only at the factory, and applies when an equation requires a correction term using a parameter which the logger does not measure. In this case, the default parameter set by the command settings will be used.
The dependent equations are explained by example on the following pages. For a first reading, it is suggested they are studied in order, as new concepts are introduced progressively, and some of the later examples are more complicated.
- Example 1: corr_pH - Simple temperature correction of pH
- Example 2: corr_pH - pH correction without Temperature
- Example 3: corr_pres2 - Temperature correction of Pressure
- Example 4: corr_cond - Conductivity corrections
- Example 5: corr_rinko - Correction of Rinko Dissolved Oxygen using Rinko Temperature sensor
- Example 6: corr_rinkoT - Correction of Rinko Dissolved Oxygen using logger Temperature sensor
- Example 7: pss78 - derivation of Practical Salinity (1978)
- Example 8: seapres - derivation of sea pressure from pressure
- Example 9: depth - derivation of depth from pressure
- Example 10: corr_metsmeth - Temperature correction of METS methane output
- Example 11: corr_rinkoB - Correction of Rinko Dissolved Oxygen using Rinko Temperature sensor
- Example 12: corr_rinkoTB - Correction of Rinko Dissolved Oxygen using logger Temperature sensor
- Example 13: Speed of Sound
- Example 14: deri_speccond, specific conductivity
- Example 15: deri_bprpres and deri_bprtemp channels
- Example 16: distancefromechotiming Distance from echo timing
- Example 17: corr_o2conc_garcia, O2 concentration compensated for salinity and pressure
- Example 18: deri_o2sat_garcia, Derived O2 saturation from concentration