ALPHA-VISION® HowTo: Graphs

Graphs

SUMMARY

It is described how to set up graphs.

CONTENTS

1. Task formulation
2. General information about a graph.
3. Defining a graph
4. Scaling of the Time-Axis
5. Automatic start of the Graph
6. Displaying values stored in the Buffer
7. Hints & Tips

Task formulation

A continuous sinus (Peak amplitude ±1; period 90 sec) should be recorded.

• The graph should show a 3 minute clipping.
• The time axis (x) of the graph should be scaled with the apposite time.
• Recording of the measuring point should start on system start.
• It should be possible to stop the running graph.
• It should be possible to move the time axis of the graph in the past; at least for 10 minutes, by steps of 1 minute.

General information about a graph.

A graph is a rectangular area wherein a sequence of numerical values displayed as a polygon or a series of dots in dependency of the time. (y=f(t))

A graph got a buffer (ring-buffer in the memory) of a defined size. The measuring value is checked every second, but only changes are saved.

In the graph the values are displayed in equal time distances of one second.

A graph may run to the right, left, up or down.

It is possible to position several graphs above each other.

Defining a graph

Select the item "Graph" via the AbvEditor pull-down menu Insert.
With the mouse pointer which has changed to a hair-cross pull up the wanted size for the graph.

Via AbvEditor_PDM Edit "Attributes sequential" the following categories have to be defined:

• Variables
  Define the function Obj_Value(SINUS) .
  (SINUS is the name of the Data Object its value should be shown in the graph.)
  
  
• Format
  Select direction "Left" Graph style "Polygon".
  (Direction left: Value "moves" to the left, the latest value stays at the right hand side. (standard for time axis))
  (Polygon: The values are shown as consecutive line)
  
  
• Scaling
  Scaling offset function Y: Usr_Const(-1)
  (Since a negative value (-1) should be displayed the base line must be moved by -1)
  (-) minus = moves it up
  (+) plus = moves it down
  
  Scaling range function Y: Usr_Const(2)
  (Due to the peak values from -1 to +1 the scaling range is 2)
  
  Scaling offset function X: Obj_Value(TSTART)
  (The System Object "TSTART" got the value: 'actual time' minus 'scaling range in seconds'. It represents the oldest point of time displayed in the graph; it is incremented by 1 every second.)
  
  Scaling range function X: Usr_Const(180)
  (Defines 180 seconds (3 Minutes) for the scaling range)
  
  Pool size:600
  Defines the number of measuring value changes that can be stored.
  (If the measuring value changes every second it is possible to store values for 600 seconds = 10 Minutes.
  In case the changes are rarely the period of time values are recorded for is elongated.)

Scaling of the Time-Axis

Select the item "Digital Meter" via the AbvEditor pull-down menu Insert . With the mouse pointer which has changed to a hair-cross pull up the wanted size for the digital meter.

Via "Attributes sequential" the following categories have to be defined:

• Variables
  Obj_Value(TSTART)
  (Displayed is the value of the System-Object "TSTART", together with the defined offset it provides the wanted scale labeling.)
  
  
• FORMAT: ho:mi:se
  (Defines that the value of "TSTART" is displayed in the time format "hour:minute:second")
  
  
• SCALING:
  Offset Funktion: Usr_Const(n)
  (Depends on the position of the digital meter along the X-Axis; the TSTART-Value represents the oldest time value)
  
  • Left Digital Meter:
    Shows the oldest point of time -> Offset = 0
    
  • Digital Meter in the middle:
    Shows the point of time right in the middle (TSTART-Value + 90 sec) -> Offset = 90
    
  • Right Digital Meter:
    Shows the actual point of time (TSTART-Value + 180 sec) -> Offset = 180

Automatic start of the Graph

In the AbvBrowser Pull-down menu 'File' - item 'Global events' for the System event:

• "On Startup"

the following actions have to be defined:
Obj_TickOn(TSTART,180); Obj_SetSts(TSTART,1)

Means:
The System-Object "TSTART" is set to the value of the actual time minus 180 (seconds, the scaling range).

The status of the System-Object "TSTART" is set to 1.
(Status "1" signalizes ‘Graph is running’, "0" signalizes ‘Graph has stopped’; this information is used to manage the operability of the control buttons, see next chapter.)

Displaying values stored in the Buffer

The graph area shows the measuring values stored in the buffer for the past 3 minutes.
To display earlier values stored in the buffer:

• The running graph must be stopped.
• The Time-Object "TSTART" must be set to the wanted Display-Time.

(When starting the runtime this is the only button accessible.)

Via AbvEditor_PDM Edit "Attributes sequential" the following categories have to be defined:

• Action:
  Obj_TickOFF(TSTART) ; Obj_SetSts(TSTART,0)
  The second-wise incrementing of the System-Object is stopped i.e. the running graph is halted.
  Note:

  
  Querying the measuring value and saving changes is not affected, it can’t be stopped.
  
  The status of the System-Object "TSTART" is set to "0" to signalize "graph has stopped"
  
  
• Enable:
  Obj_StsCmp(TSTART,1)
  The status is compared with the value "1", on ‘true’ (Graph running) the value "1" is returned.
  Note:

  Any value beside "0" enables the button, it is accessible.

(In runtime only accessible if the graph has stopped.)

Via Edit "Attributes sequential" the following categories have to be defined:

• Action:
  Obj_DecrData(TSTART,Value,60)
  The value of System-Object "TSTART" is decremented by 60.
  (With any pressing of the button the Time-Axis of the graph is moved to the right (into the past) by one minute; the digital meter for the scale indication are showing the appropriate time, since they also reverence to the System-Object "TSTART".)
  
  
• Enable:
  Obj_StsCmp(TSTART,0))
  The status is compared with the value "0", on ‘true’ (Graph stopped) the value "1" is returned - enabled.

(In runtime only accessible if the graph has stopped.)

Via Edit "Attributes sequential" the following categories have to be defined:

• Action:
  Obj_IncrData(TSTART,Value,60)
  The value of System-Object "TSTART" is incremented by 60.
  (With that button the Time-Axis is moved in the opposite direction)
  
  
• Enable:
  Obj_StsCmp(TSTART,0)
  Graph stopped? - enabled

(In runtime only accessible if the graph has stopped.)

Via Edit "Attributes sequential" the following categories have to be defined:

• Action:
  Obj_TickOn(TSTART) ; Obj_SetSts(TSTART,1)
  The second-wise incrementing of the System-Object "TSTART" is initiated, the graph starts running.
  Note:

  Incrementing starts with the actual time, the measuring values saved in the meantime are inserted timely.
  
  
  The status of the System-Object "TSTART" is set to "1" to signalize "Graph is running".
  
  
• Enable:
  Obj_StsCmp(TSTART,0)
  Graph stopped? - enabled

Hints & Tips

It is possible to use the same graph to show the value trend of different Data-Objects, as far as the defined scalings do fit. The Data-Objects in question may be referenced statically when creating the project or dynamically in runtime.

See thereto: Referencing to Data Objects

A Graph usually displays measuring data read from the Short Term Archive (described above), but it is also possible to supply it with data out of the Long Term Archive.

See also: Archiving Data

The definition from which archive the measuring values should be read is done via the <ApplyGroup>.
To the category "Action" of the graph an entry for "Apply group" is added. The Name defined for "Apply group" is arbitrary, it merely relates graph and archive.

The connection graph to archive type is done via a button with the following action:
"Grfx_SetVarHist(<ApplyGroup>,n)"

Example:

Grfx_SetVarHist(SINUS,1)		
(The graph with the Apply Group "SINUS" is switched to the Long Term Archive)

Grfx_SetVarHist(SINUS,0)		
(The graph with the Apply Group "SINUS" is switched to the Short Term Archive)		
		

Bound to a Digital Meter the following function:

"Grfx_GetVarHist(<ApplyGroup>)"

returns information about the archive actually shown in the graph.

• 0 = Short Term Archive
• 1 = Long Term Archive