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andyhill

Data Concentrator

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Generic Question : On larger systems with multiple PLC's of the same brand doing there thing( say 5 machines all on Allen Bradley) OK to get the HMI to talk to all 5 machines it would be better to put in a data concentrator but what is the consensus on the platform for the data concentrator. A) a "Server" running some gateway app like Kepserver and link master etc or B) a PLC based data concetrator with interfaces out as required.

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If you have 5 PLC's then you could use one Kepserver to connect to all 5 on individual channels. This allows the server to talk to the devices simultaneously. The HMI is then connected to the server. The server is a single connection point for the HMI. In this case you are get the data as it comes from the device. LinkMaster would come in to play if you had multiple OPC servers and you wanted to provide one connection point to the HMI for all the servers. You can do this bacause LinkMaster is a both a client and a server. We see it used mostly in sitatuations where customers wish to control the access to the OPC servers. You can set a poll rate in the LinkMaster Link groups and that is the rate data is polled. If clients connect to LinkMaster and request data from the Link items at a faster rate the will be updated from the cache, LinkMaster will not transalte the request down to the server. The other advantage is that connected clients only have access to the Link Items, they cannot get data from the OPC servers that has not been configured in LinkMaster allready so you have an added level of security. You must keep in mind though that data is update from cache not from the device. However if you set the client update fast enough you will get and changed data from the server as soon as it comes into LinkMaster. If you use a PLC as a concentrator it is much like LinkMaster you are relying on the concentrator to get the data in a timely manner so that the HMI may be updated. That said I have some very big customers that are using either LinkMaster or PLC's as concetrators with the same results. I think it is really a matter of the amount of work you wish to put into it and what you feel most comfortable with. Edited by Tech Fred

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If you are using wonderware, you could check out their DAS servers. I have used them before (DASABTCP) and they work great. If you are using intouch 10+ or system platform, you can set up redundancy too. Edited by Camel

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