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OPC-UA Client - Instance & item setup

How to setup an OPC-UA Client in SIA

Written by Paul Bendixen

Updated at April 23rd, 2025

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Table of Contents

Parameters Instance Keys and certificates Accepting certificate on OPC-UA server Item

Articles in this section:

  • OPC-UA Client - Instance & item setup
  • OPC-UA Client - Troubleshooting

Table of Contents

ParametersInstanceKeys and certificatesItem

Parameters

When using the OPC-UA Client Connector both the instance and item have specific parameters. These parameters are required as they are needed to establish connection and to identify which objects to read from.


Instance

The instance needs the following parameters to establish a connection to the OPC-UA Server:

Parameter Description
Address The address of the server, including endpoint
opc.tcp://75.152.105.54:48010/myEndpoint
User name The user name to use when connecting to the server, leave blank for connecting without username/password
Password The Password to use with the username
Security Mode The security mode used for connecting with the server. Supported security modes:
  • None
  • Sign
  • Sign & Encrypt
Security Policy Security policy mode used by the OPC-UA server for encryption. Supported policies:
  • None
  • Basic128Rsa15
  • Basic256
  • Basic256Sha256
Timestamp Whether to use the servers timestamp or SIA Connect's local timestamp given by the time of when the value was read
Certificate Connection certificate used to establish a secure channel to the OPC-UA server. Certificates can be uploaded by follow these steps:
Manage files for Connectors‍  
Key Connection key used to establish a secure channel to the OPC-UA server. Keys can be uploaded by follow these steps:
Manage files for Connectors‍ 


Keys and certificates

Delete

Accepting certificate on OPC-UA server

If the OPC-UA server is configured with an encrypted connection (security policies & mode is set) the OPC-UA server needs to accept the connection certificates from SIA Connect in order to establish connection.

On first boot the Connector will generate a certificate and key to be used with connecting, these certificates is used for secure connections to the OPC-UA server and needs to be accepted on the server side. The certificates can be downloaded from the Connectors page under files by following this guide Manage files for Connectors.‍

Item

The item parameters that are needed to connect to the objects in the OPC-UA server

Parameter Description
Identifier The identifier to adress the item. The connector will figure out whether it is a numeric, guid or string (in that order)
eg with namespace included: 
  • ns=2;i=456
  • ns=2;s=MyOPC.UA.Tag
  • ns=2;g=1d545837-3edb-43f5-a4b8-073c0775fcbe
or if namespace is already given in the Namespace indexparameter.
  • 456
  • MyOPC.UA.Tag
  • 1d545837-3edb-43f5-a4b8-073c0775fcbe

Reading arrays

When reading arrays, the index of the array must be specified in the identifier:

  • ns=2;i=456[0]
  • ns=2;s=MyOPC.UA.Tag[0]
  • ns=2;g=1d545837-3edb-43f5-a4b8-073c0775fcbe[0]
Floating Point Precision
Represents the amount of digits following the decimal-point in floating point values
Access Level  Current read/write
Read and write the current value of the tag
History read
Read the tag's historical data. All values stored within the given time will be read, presented as an array of JSON objects
History From
History read from time in Epoch time
Can be used either with a static Epoch timestamp, or with a negative value representing the amount of milliseconds from the current time
History To  History read to time in Epoch time
Can be used either with a static Epoch timestamp, or with a 0 representing the current time
History No Value Handling
Keep latest non-empty value
If there is no historical value in the time-constraints, SIA will retain the latest value - even if the latest value is older than the time given
Use empty value
If there is no historical data in the time-constraints, the item will have an empty value



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