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AV_96564903-Newcomer
3-Newcomer
March 9, 2023
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Question related to Scan class, compression in OPC

  • March 9, 2023
  • 1 reply
  • 1830 views

Hello, I have few questions related to OPC configuration in Kepware. Appreciate your answers

1. In kepware , Are there any ways to specify/customize the deadband at Tag Level? ( currently deadband property is on the group level )

2, For float data type , what is the max precision available . Is this configurable . Currently, In OPC Client I see only 3 decimal places ( example 10.213) 

3.If the poll/exception update rate is 1000ms and MaxItem per Read is 512 ,  are all the 512 tags updated every 1000ms in that group? . What if there are more than 512 Tags in that group?

Thanks in advance

Anbu veerappan

 

 

 

Best answer by MRohilla

Greetings!!

1- no, when using the OPC UA Client driver, each Device object declares a single Deadband for all items added to this device. Users can create more device objects below the same channel (or more channel/device combinations) and set other deadbands.
2- kepware OPC UA Client driver and OPC server interfaces do NOT truncate or round floating point values. the maximum precision available is the full precision of the entire float data type. Typically, OPC clients that visualize float data values simply arbitrarily truncate the full resolution for visual aesthetic. in other words, the client that is only displaying 3 levels of precision should actually be receiving the full resolution and arbitrarily chopping every else off beyond 3. To see the floating point delivered to the client, one can enable OPC UA diagnostics in Project Properties and launch the OPC Diagnostics Viewer via Tools -> View OPC Diagnostics.
3- max items per read is only relevant in Poll Mode (not relevant in Exception Mode). In Poll Mode, the OPC UA Client driver groups all 512 tags into the same read request. If morethan 512 tags are referenced from a single Kepware OPC UA Client driver Device object, then the additional tags beyond 512 will be grouped together in a second read. The driver will attempt to obtain all new values for all referenced tags every 1000 ms.


Regards,

Mohit

1 reply

M
MRohilla12-AmethystAnswer
12-Amethyst
March 13, 2023

Greetings!!

1- no, when using the OPC UA Client driver, each Device object declares a single Deadband for all items added to this device. Users can create more device objects below the same channel (or more channel/device combinations) and set other deadbands.
2- kepware OPC UA Client driver and OPC server interfaces do NOT truncate or round floating point values. the maximum precision available is the full precision of the entire float data type. Typically, OPC clients that visualize float data values simply arbitrarily truncate the full resolution for visual aesthetic. in other words, the client that is only displaying 3 levels of precision should actually be receiving the full resolution and arbitrarily chopping every else off beyond 3. To see the floating point delivered to the client, one can enable OPC UA diagnostics in Project Properties and launch the OPC Diagnostics Viewer via Tools -> View OPC Diagnostics.
3- max items per read is only relevant in Poll Mode (not relevant in Exception Mode). In Poll Mode, the OPC UA Client driver groups all 512 tags into the same read request. If morethan 512 tags are referenced from a single Kepware OPC UA Client driver Device object, then the additional tags beyond 512 will be grouped together in a second read. The driver will attempt to obtain all new values for all referenced tags every 1000 ms.


Regards,

Mohit

    A
    AV_96564903-NewcomerAuthor
    3-Newcomer
    May 12, 2023

    Thanks for your response. Yes. they are accepted solutions . 

    Also, I have one new question. Please clarity /answer and move it to separate topic if appropriate . 

     

    In Kepware ( KepSever Ex 6 server configuration ) what is the suggested Device level scan mode? What settings are appropriate to scan 1000s of tags under each device ?  

    • Request all data at Scan Rate Vs  Respect Client Specified Scan Rate

    What are the pros and cons of the above settings on overall impact . If you need more info, please email

     

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