Transfer Function Manipulation
The following sections provide more detail on various input parameters for the XY Transfer Function, XYZ Transfer Function and the XY Table components.
Although the actual entered X, Y and Z data must remain constant throughout the run, there are various input parameters that may be used to manipulate the transfer function on-line:
XY Characteristics:
X-Axis Offset or Phase Shift: This value is subtracted directly from the X-axis data points. Thus, data (1.0, 8.0); (2.0, 9.0) with an X-Axis Offset of 1.0 is equivalent to: (0.0, 8.0); (1.0, 9.0). This is equivalent to adding a phase shift to the waveform, where a positive value causes a leading phase shift.
Y-Axis Offset or DC Offset: This value is added directly to the Y-axis data points. Thus, with a Y-Axis Offset of 1.0 (and X-axis offset of 0.0), the output, for an input of 2.0, would be 10.0. This offset is added to the output after it is multiplied by the Y-axis gain (explained below) so that if you change the sign of the Y-axis gain, the waveform flips horizontally without any vertical jump.
X and Y-Axis Gains: All X and Y coordinates are multiplied by these respective factors. The gains do not multiply the offset values.
XYZ Characteristics:
X-Axis Offset or Phase Shift: This value is subtracted directly from the X-axis data points. Thus, data (1.0, 8.0, 9.0); (2.0, 9.0, 11.0) with an X Offset of 1.0 is equivalent to: (0.0, 8.0, 9.0); (1.0, 9.0, 11.0). This is equivalent to adding a phase shift to the waveform, where a positive value results in a leading phase shift.
Y-Axis Offset or Phase Shift: This value is subtracted directly from the Y-axis data points. Thus, data (1.0, 8.0, 9.0); (2.0, 9.0, 11.0) with a Y Offset of 1.0 is equivalent to: (1.0, 7.0, 9.0); (2.0, 8.0, 11.0). This is equivalent to adding a phase shift to the waveform, where a positive value results in a leading phase shift.
Z-Axis Offset or DC Offset: This value is the offset that is directly added to the output and is added to the output following a multiplication by the Z-Axis Gain (explained below). The default value of the Z-Axis Offset is zero.
X, Y and Z-Axis Gains: All X, Y and/or Z coordinates are multiplied by these respective factors. The gains do not multiply the respective offset values.
There are two methods by which to enter the coordinate points: One method is to enter the data directly into a table in the component input parameters. The other is to provide the required values through an external ASCII text file.
NOTE: The table data entry method is only available in the XY Characteristics and XY Table components. The XYZ Component allows data entry by external ASCII file only.
XY Characteristics:
If entering coordinates from an external ASCII data file, a certain structured format must be followed. Descriptive comments may only be placed at the beginning of the file, provided they are preceded by an exclamation point '!'.
An example ASCII data file is given below:
|
! Input data for XY Characteristic ! 1.0 8.0 2.0 9.0 3.0 10.0
|
NOTE: If Output Mode | Interpolated is selected, the X data points must be entered in ascending order.
XYZ Characteristics:
A certain structured format must be followed when constructing the ASCII data file. Descriptive comments may be placed anywhere in the file, provided they are preceded by an exclamation point '!'. You need to place one of the keywords 'XDATA:', 'YDATA:' or 'ZDATA' at the beginning of each respective coordinate section of the data file. Also, an 'ENDFILE:' command must be placed at the end of the file.
If you have N, X-coordinates and M, Y-coordinates, then you must include M x N, Z-coordinate points. If the number of Z-coordinates is less than M x N, and error will occur. If greater than M x N, the extra points will be ignored.
An example ASCII data file is given below:
|
! Input data for XYZ Characteristic ! XDATA: 1.0 2.0 ! ! More comments ! 3.0 YDATA: 7.0 8.0 9.0 ZDATA: 7.0 8.0 9.0 14.0 16.0 18.0 21.0 24.0 27.0 ENDFILE: ! |
NOTE: If Output Mode | Interpolated is selected, the X data points must be entered in ascending order.
XY Table:
If entering coordinates from an external ASCII data file, a certain structured format must be followed. Descriptive comments may be placed anywhere in the file, provided they are preceded by an exclamation point '!'.
An example ASCII data file is given below:
|
! Input data for XY Table ! ! X Y1 Y2 ..... Y10 0.0 0.01 0.02 ... 0.1 1.0 1.01 1.02 ... 1.1 2.0 2.01 2.02 ... 2.1
|
NOTE: If Output Mode | Interpolated is selected, the X data points must be entered in ascending order.
XY Characteristics:
There are two output modes available: Interpolate or Sample and Hold. When the X input falls on one of the discrete points, Y is the corresponding point from that (X,Y) pair. Otherwise, the Y value is chosen depending on the selected mode.
Interpolate: The output is linearly interpolated between adjacent transfer function coordinate points. For example, if the coordinate points are (1.0, 8.0) and (2.0, 9.0), and the input is 1.5, then the output would be 8.5. Inputs smaller than the first point or larger than the last point will be extrapolated using the slopes the first or the last data segment, respectively.
Sample and Hold: The output corresponds to the transfer function coordinate point that is immediately after the input. For example, if the coordinate points are: (1.0, 8.0); (2.0, 9.0) and the input is 1.5, the output would be 9.0. Inputs smaller than the first point or larger than the last point will have the outputs corresponding to the first or the last data point, respectively.
XYZ Characteristics:
There are two output modes available: Interpolate or Nearest Data Point. When the X and Y inputs fall on one of the discrete points, Z is the corresponding point from that (X,Y,Z) point. Otherwise, the Z value is chosen depending on the selected mode.
Interpolate: The output is bi-linearly interpolated between adjacent transfer function coordinate points. For example, if the data points are: (1.0, 8.0, 9.0); (2.0, 9.0, 11.0) and the input is (1.75, 8.75), the output would be 10.5. Inputs smaller than the first point or larger than the last point will be extrapolated using the slopes the first or the last data segment, respectively.
Nearest Data Point: The output corresponds to the transfer function coordinate point that is nearest to the input. For example, if the data points are: (1.0, 8.0, 9.0); (2.0, 9.0, 11.0) and the input is (1.75, 8.75), the output would be 11.0. Inputs smaller than the first point or larger than the last point will have the outputs corresponding to the first or the last data point, respectively.
XY Table:
There are two output modes available: use interpolation or nearest data point. When the X input falls on one of the discrete points, Y is the corresponding point from that (X,Y) pair. Otherwise, the Y value is chosen depending on the selected mode.
use interpolation: The output is bi-linearly interpolated between adjacent coordinate points. For example, if the data points are: (1.0, 8.0, 9.0); (2.0, 9.0, 11.0) and the input is (1.75, 8.75), the output would be 10.5. Inputs smaller than the first point or larger than the last point will be extrapolated using the slopes the first or the last data segment, respectively.
nearest data point: The output corresponds to the transfer function coordinate point that is nearest to the input. For example, if the data points are: (1.0, 8.0, 9.0); (2.0, 9.0, 11.0) and the input is (1.75, 8.75), the output would be 11.0. Inputs smaller than the first point or larger than the last point will have the outputs corresponding to the first or the last data point, respectively.
Related Topics