Topic: DMD0244 The PID View |
|
The PID View is where the majority of the work related to configuring, tuning, and monitoring PID loops will be done. The PID View is opened by selecting Debug-> PID View from the Online Toolbar, or right-clicking on any PID instruction in a ladder diagram and selecting Trend Instruction from the pop-up menu, or double-clicking on the PID Overview graphic for that PID loop.
If the project contains more than one Closed Loop Controller (PID) instruction the PID View dialog needs to know which PID loop to display in the view. The Select PID Loop dialog will contain a list of the PID loops in the project, select the loop to display from the list.
The PID View is broken into three sections: one down the left side (the PID Data form) that displays the current configuration of the underlying PID Loop, and on the right side there are two trend graphs (one with the .PV and .SP fields, and one with the .Output and .Bias fields).
|
|
Entries in PID Data FormPID Struct - The text displayed in the upper left corner is the Struct name of the current PID loop. If the Setpoint of that PID Loop is being driven by a Ramp/Soak Profile, the Struct name of that Ramp/Soak profile along with the current step in that profile will be displayed.
PID Loop: - selects which PID Loop to display. If one or more PID View tabs are already open, the following dialog will be displayed. This dialog allows the new PID view to be opened in one of two ways:
Auto-Tune ... - will open the dialog to initiate an Autotune cycle for the currently selected PID Loop. The Autotune process is explained in more detail in the Using the Auto-tune Process help topic.
Mode: - displays the mode of the currently selected PID loop (Auto / Manual / Override Auto / Override Manual)
PLC Mode: - displays the current mode of the controller (Run / Program / Debug).
Override Mode - the checkbox enables and disables the Override option. Override mode allows the PID View to change the loop's mode (Auto / Manual) independent of the input leg to the Closed Loop Controller (PID) instruction. If Override is enabled (checked) the drop-down list will allow the user to select between Auto and Manual mode.
Tuning Parameters - this group displays the current values for Gain (P), Reset (I), Rate (D), and the Sample Time (ms).
The 'Load from PLC' and 'Save to PLC' buttons allow for runtime monitoring and changing of these values. All 4 of the values will be read from the controller or written to the controller when you select 'Load From PLC' or 'Save to PLC' operations.
Variables - this group displays the current values for the Process Variable (PV), Setpoint (SP), the Output value, and the Bias value.
The 'Load from PLC' and 'Save to PLC' buttons are primarily for managing these values when the loop is in Manual mode.
|
|
PID View Toolbar Button DescriptionsThe PID View contains it's own toolbar with buttons that are specific to the PID View and PID configuration and troubleshooting operations.
The function of each of these buttons - from left to right across the toolbar - is described below:
|
|
|
Select Time Range - designates how much data to export, this can be either all of the data accumulated since the PID View was opened, or a range specified by a start time and an end time.
Start Time - specifies the beginning
of the data to export
Ending Time - specifies the
end of the data to export
Confirm Selections - will display the range of data points to export to the file.
|
|
|
|
Record Current PID Loop ValuesThe next two buttons allow for instantaneous logging of the data point values currently being displayed on the trend graphs to disk. The recorded data is similar to that of Export Data as described above but this copy has a fixed format where each field is enclosed in double quotes and separated by commas. For example: "2012/5/17","13:52:37.047","MyPID.PV","0.35" "2012/5/17","15:48:02.160","MyPID.SP","0.62" "2012/5/17","13:35:23.088","MyPID.Bias","0.035" "2012/5/17","13:39:19.472","MyPID.Output","0.73" "2012/5/17","12:02:54.819","C10","off" "2012/5/17","12:02:54.819","C11","off" "2012/5/17","12:02:54.819","C12","off" "2012/5/17","12:02:54.819","C13","off"
Begin Recording - click this button to begin the recording session, The button face will change to a black square and the word [RECORDING] will be displayed in the dialog's tab.
Stop Recording - will stop the data recording process, and a 'Save As' dialog will prompt you for the filename in which to save the recorded data.
Pause Recording - stops recording data while the button is depressed. The button will appear depressed and the word [RECORDING - PAUSED] will be displayed in the dialog's tab. Click the button again to continue recording data, or click the cancel button to stop the recording session completely.
|
|
|
The Crosshair Cursor
The cross-hair is displayed anytime the mouse cursor moves over any of the panes in the PID View. The cross-hair provides a visual reference when comparing values displayed on the Panes.
If there are multiple Panes in the PID View, the vertical bar of the cross-hair will extend through all of them. Using the Cross-hair Zoom In / OutUsing the CTRL key and the scroll wheel on the mouse will put the PID
View into Historical Mode and zoom into
or out of the area under the center of the cross-hair as follows:
Using the Cross-hair to Snapshot DataLeft-clicking the mouse will take a snapshot of all the values on all of the Panes on the Trend at the time where the cross-hair was located, then present that data on the snapshot dialog.
Clicking the Copy Contents to Clipboard button will copy the data displayed on the snapshot dialog to the Windows clipboard, which can then be pasted into any other Windows application for further processing.
|
|
PID View Global Display OptionsAllows the user to specify the colors, line styles for the trend panes in the PID View and also configure the memory usage limits for the PID View. The PID View Global Options dialog can be accessed by selecting the View -> Options from the menu then clicking the PID View tab, or selecting Global Options from the right-click menu of the PV/SP Pane.
Apply Options to - which Views
will be affected by changes to this dialog
Pane - specifies which pane of the PID View to modify
Background Color - specifies the area surrounding the trend displays
Trending Area Color - specifies the background color of the trend displays themselves
Grid Lines/Tick Marks - specifies
colors and the scale used to display the grid in the trend display area Value Scale - specifies values for the vertical scale
Time Scale
- specifies the colors and the scale (Time) used to display the grid in
the trend display area
Variable
Colors - specifies the background color for the PID loop variables
in the PV/SP Pane and the Output Pane
Show Text on Toolbar Buttons - if checked, toolbar buttons will display the icon and the button name. if unchecked only the icon will be displayed.
Prefer Nicknames to Element Names - if the elements being exported have nicknames assigned to them, the nicknames will be in the export file instead of the element. For example, if C13 has the nickname "Low Low Alarm", the exported lines for this data point would be "2012/5/17","12:02:54.819","Low Low Alarm","off"
Restore Defaults - click to restore default values for all of the PID View Global options.
Export / Logging Options - defaults used in the Export and Logging functions
Specify decimal places for floating point data - enable this option to override the default handling of the number of decimal places displayed for floating point values and always display the same number of decimal places as selected.
Delimiter - designates what character will be used to separate the individual elements on each exported line of data. The default is a comma between each element on a line.
Enclose in Quotes - designates which elements need to be enclosed in double-quotes
Export/Logging Method - specifies the format of the output data
Historical
Data - designates the amount of memory limit for saving trend data
if Historical Trend Mode is enabled.
|
|
See Also:
Process Control Instruction Set
The PID View
Using the PID Process Simulator
|
|
Related Topics:PID Calculation and Tuning Constants
PIDINIT - Set PID Tuning Constants Alarm HandlersInput and Output Value LimitersDEADBAND - Set Outside Deadband Noise SuppressionINTEGRAT - Integrate Over Time Ramp/Soak Profiles - up to 250 steps per ProfileInput and Output ScalingAnalog Control using a Discrete OutputTIMEPROP - Time Proportional Control
|
|