Dependent equations

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 that 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 examples 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.