Create a reference curve math with a new math channel - vector reference curve.
Open the settings for the vector reference curve and select the channel that will be used for checking the level (CylPressure).
Linear interpolation will give a smoother transition between points on the curve.
Check signal bounds will create an additional output channel which will output 1 when the input is higher than the reference curve and wil output 0 when the input is below the reference curve.
The reference curve is defined with a table. The first column is crank angle (X) axis, and the second column the amplitude of the reference (Y) axis. In this first example, we have defined only two points with a value of 41 (bar).
We have added a CA scope and selected the cylinder pressure signal and reference curve for display. An indicator lamp was also added and the output channel from the vector reference curve assigned to it. When the pressure is above the reference curve the indicator lamp will turn red, otherwise, it stays green. The output from the channel goes from 0 to 1, when the reference axis is crossed.
We can modify the simple reference curve. It is also very easy to create a refence curve from a recorded pressure signal. For this we need some datafile with the pressure signal that will be used as reference.
First, we add a basic statistics math channel.
We open the basic statistics setup and select the pressure channel from the combustion analysis module (combustion analysis must be added in order to have crank-angle domain instead of time domain). Maximum should be selected to get the maximum value of all the cycles and under calculation type time based and single value.
When we add this new channel on the CA scope we see that we get the maximum value of pressure from all the cycles.
Now we need to make an offset curve that will be used as a trigger. As an example, we will make a curve that will trigger the vector refence curve output channel when the maximum pressure is above 110%.
We create a new formula where we multiply the previous basic statistics channel with 1.1.
Next step is to display only the last created formula on the CA scope and copy the data to clipboard.
We open again the vector reference curve setup and simply paste the values.
It is also possible to reduce the number of points for the reference curve in Excel.
Copy the data to excel and use the formula =OFFSET(Sheet2!A$1,(ROW()-1)*100,0) to output only every 100th line. This will make modifying the refence curve much easier since there will be only 37 points left instead of 3600.