What does the "| n" mean when viewing the properties of an OPC variable in Vista workstation?

[Product_Support]

Issue

• What does the "| n" mean when viewing the properties of an OPC variable in Vista workstation?
• Problems have been encountered with OPC variables
• Error messages such as "The object is no longer available in the servers address space",
• Also, canonical data type or OPC data types.

Environment

Vista 5.1.X

TAC Vista OPC client

Cause

The "|n" is a reference to the data type or canonical data type as it's called in the OPC standard. In the world of OPC, the client application can be created in on one of many diverse programming languages. To resolve potential issues all OPC data types are assigned a specific Canonical Data Type. When a client application adds an OPC Item to an OPC Group it can use the default data type for the item or it can request the item with a specific canonical data type. If the OPC tool is used then the canonical is added automatically by checking with the server. It's only if variables are added manually that this information is required.

Resolution

The method used for addressing OPC variables is Folder.Variable_Name|Data_Type

 The table below details the data types: 

Data Type	Canonical Type	Size	Data Range
Boolean	11	1 Bit	True or False
Byte	17	1 Byte	0-255
Byte Array∗	8209	1 Byte times Array Size	0-255
Short	2	2 bytes	-32768 – 32767
Short Array∗	8194	2 bytes times Array Size	-32768 – 32767
BCD	18+	2 bytes	0 - 9999
BCD Array∗	8210	2 bytes times Array Size	0 - 9999
Word	18	2 bytes	0 – 65535
Word Array∗	8210	2 bytes times Array Size	0 – 65535
Long	3	4 bytes	-2,147,483,648 to 2,147,483,647
Long Array∗	8195	4 bytes times Array Size	-2,147,483,648 to 2,147,483,647
LBCD	19+	4 bytes	0 - 99999999
LBCD Array∗	8211	4 bytes times Array Size	0 - 99999999
Dword	19	4 bytes	0 – 4,294,967,295
Dword Array∗	8211	4 bytes times Array Size	0 – 4,294,967,295
Float	4	4 bytes	-(3.40 E38 – 1.40 E-45) to (1.40 E-45 – 3.40 E38)
Float Array∗	8196	4 bytes times Array Size	-(3.40 E38 – 1.40 E-45) to (1.40 E-45 – 3.40 E38)
Double	5	8 bytes	-(1.798 E308 – 4.941 E-324) to 4.941 E-324 – 1.798 E308)
Double Array∗	8197	8 bytes times Array Size	-(1.798 E308 – 4.941 E-324) to 4.941 E-324 – 1.798 E308)
Char	16	1 Byte	All Characters supported in the standard ASCII table
String	8	1 – n Bytes	All Characters supported in the standard ASCII table