|
|
|
|
|
|
  Reading Tags using OPC Web Client ActiveX Controls
Quick links within this page:
Objective
To show OPC Tag values within a web-page.
Source Code for reading a single Tag:
 VBscript
<HTML>
<head>
<title>OPC Web Client Example, Single Tag Read Within Internet Explorer</title>
</head>
<body>
<p>
<input type="text" name="T1" size="20">
<input type="button" value="Button" name="B3">
</p>
</body>
<script language="vbscript">
sub b3_onClick
set opcwebclient = CreateObject("
OPCLabs.EasyDA3.0")
set valueTimeQuality = opcwebclient.ReadItem("", "OPCLabs.KitServer.2", _
"Simulation.Random", "", 0)
if Err.Number = 0 then
document.all.t1.value = valueTimeQuality.Value
else
msgbox "An error occurred: " & Err.Number
end if
end sub
</script>
</html>
Simply place the above text under the "</body>" HTML tag and then save your HTML page. Now open that web-page directly from Internet Explorer and then click on the button.
JAVASCRIPT
<HTML>
<head>
<title>OPC Web Client Example, Single Tag Read Within Internet Explorer</title>
</head>
<body>
<p>
<input type="text" name="T1" size="20">
<input type="button" value="Button" name="B3" onClick="doRead();">
</p>
</body>
<script language="javascript">
function doRead()
{
try
{
var opcWebClient = new ActiveXObject("OPCLabs.EasyDA3.0");
var valueTimeQuality = opcWebClient.ReadItem("", "OPCLabs.KitServer.2",
"Simulation.Random", "", 0)
document.all.T1.value = valueTimeQuality.Value;
}
catch(e)
{
alert(e)
}
} </script>
</HTML
With the above modification set, and with the Javascript code present, you can now save this web-page and load it directly into the web-browser.
Source code for reading multiple Tags in one transaction:
VBscript
<HTML>
<head>
<title>OPC Web Client Example, Read Multiple Tags Within Internet Explorer</title>
</head>
<body>
<p>
<textarea rows="11" name="S1" cols="33"></textarea>
<input type="button" value="Button" name="B3">
</p>
</body>
<script language="vbscript">
sub b3_onClick
'define an opc web client object
Dim EasyDA
Set EasyDA = CreateObject("OPCLabs.EasyDA3.0")
'define an object to receive the values, as a collection
Dim VTQs
'make the call to do the read
VTQs = EasyDA.ReadMultipleItems("", "OPCLabs.KitServer.2", _
Array("Simulation.Random", "Trends.Ramp (1 min)", "Trends.Sine (1 min)", "Simulation.Register_I4"))
'define a string to build a message with
Dim strWriteValue
strWriteValue = "Tag Read, data as follows: " & vbCrLf & vbCrLF
'iterate thru collection, reading the tag read details
'building-up a friendly message string
Dim I
For I = LBound(VTQs) To UBound(VTQs)
'is this item an error?
If VarType(VTQs(I)) <> 10 Then
With VTQs(I)
strWriteValue = strWriteValue & "Array Element #" & I & vbCrLf _
& "Value: " & .Value & vbCrLf _
& "Quality: " & .Quality & vbCrLf _
& "Timestamp: " & .TimeStamp
End With
Else
'an error happened, handle gracefully
On Error Resume Next
EasyDA.RaiseError VTQs(I)
strWriteValue = strWriteValue & "** " & Err.Source
& ": " & Err.Description & " (0x" _
& Hex(Err.Number) & ")" & " **"
On Error Goto 0
End If
strWriteValue = strWriteValue & vbCrLf & vbCrLf
Next
'write the message to the textbox
document.all.s1.value = strWriteValue
end sub
</script>
</html>
JAVASCRIPT
Feature not currently supported within Javascript due to the differences in Array handling for this development language. This feature will be made available in the next product release.
 Sign-up to our newsletter to receive product updates & other important information.
|
|
|
|
|
