Virtual Variables

Virtual Variables are used to create new calculated variables that are a mathematical function of one or more measured variables.  Virtual Variables are useful to rescale as  well as to calculate results that were not calculated in the datalogger.  Easily create an equation using variables from different Sites (dataloggers).

How does it work?

1. In db.data.browser, create new Virtual Variable, name it and associate to a Site
2. Add the new Virtual Variable to a graph
3. When browsing that graph, the results for the Virtual Variable are calculated on the fly and added to the graph.

 

Example:

Convert Air Temperature from celsius to fahrenheit.

Equation for converting Air Temp celsius to fahrenheit.


Graph showing the original measurement for Air Temperature in °C and the Virtual Variable showing Air Temperature in fahrenheit.

 

Convert a Floating Point variable to an Integer value

An easy to use wizard allows you to create your own custom Virtual Variable. Combine variables from different Sites to create cross Site averages or summaries.  Use the round function to return the integer value of a floating point value.


Graph showing the original measurement for Air Temperature in blue and the Integer Virtual Variable in red.

Total Flow from 4 sewer pumps.

Equation for calculating Total Flow.


Graph showing flow for 4 sewer station pumps, the virtual variable for Total Flow is plotted in black.

The available operators for Virtual Variable are:

+ Addition operator - Minus operator * Multiplication operator / Division operator () Parenthesis ^ Returns the value of X raised to the power of Y (X^Y). % Modulo operation. Returns the remainder of N divided by M. abs Return the absolute value round Round the argument floor Return the largest integer value not greater than the argument ceil Return the smallest integer value not less than the argument cos Return the cosine sin Return the sine of the argument tan Return the tangent of the argument acos Return the arc cosine.  Result is in Radians. asin Return the arc sine.  Result is in Radians. atan Return the arc tangent.  Result is in Radians. cot Return the cotangent rad Return argument converted to radians deg Convert radians to degrees ln Return the natural logarithm of the argument log2 Return the base-2 logarithm of the argument log10 Return the base-10 logarithm of the argument exp Returns the value of e (the base of natural logarithms) raised to the power of X. sqrt Return the square root of the argument