回應： Re: large monitoring system: MB lib, NI-OPC server, or DSC?

[ivelson]

Hi to all experts,

Our department are on the stage of assessing what will be the best way to do (or used) in our upcoming project. btw, we are developing a centralized power monitoring system in our entire plant and maybe will implement in other sites in the future.. We already finished creating LV drivers for our power meters (ADTEK devices) using LabVIEW 8.5.1 since this devices was not available in NI site. the communication protocol is Modbus RTU and the power meters have an RS-485 ports so we used serial to ethernet converter device to communicate in longer distances.

In our plant site however, we may installed more than hundreds of power meter devices to be monitored in one host computer. We need to know if it's possible if we will use our LV modbus drivers with all of this devices (i.e. 247 power meters) if each power meter needs to read/write about 60 registers at the same time? In some forums, they told about the limitations of using coils/registers was up to 100-128 registers only? is it true? we are wondering if this limitations is for the entire VI or for 1 MB master query only?

anyway, we already have NI-OPC server but have no DSC module since its very expensive. but if its the only way to have a very stable and efficient system, maybe we may adopt this. but if NI-OPC server will satisfy our requirements, we may stick to this since we already have this one in our department.

anyone here whom fully knew the advantages and drawback of each of this three items below, we are free and very glad to hear all of your comments / suggestions / solutions...

1.) MB library

2.) NI OPC server

3.) DSC module

major factors to consider:

1.) cost

2.) speed & monitoring reliability (i.e. connection & data acquire)

3.) functionality

4.) software maintenance (i.e. prog. modification)

regards,

Ivel

[ivelson]

To all LV'ers,

I knew I can search this topic in the KB of NI that tells the new features of their new module/toolkits offering. but then i decided to ask about this in the forum so i may knew and discover the ups & downs from all of your experiences. I'm very pleased to hear all your suggested solutions regarding this matter. please feel free to make comments.

thanks.

[unclebump]

Might want to look at a commercial system that is already developed.

http://www.schneider-electric.com/sites/corporate/en/solutions/energy_efficiency/quick-navigation/po...

I would definitely recommend the DSC module for the database portion of saving the info, but I guess it depends on how you want to use the system. I would also recommend using the kepware opc server for this large of a system. Might even be able to do all of it with their software. http://www.kepware.com/Products/Building_Automation_Suite.asp

Memory space could be an issue with this large of a scope. Are you planning on using window 7 for this setup. My DSC usage is still limited to the labview 7.0 version. Do you need to keep data available for a long time?? What happens with a hard drive crash??

Might be better to break it up into sections of your plant and have several systems collecting data. That way if one goes down, you don't lose your entire system. It would be best to try a single setup that is your most involved application. Make that your standard to work from.

[ivelson]

thanks unclebump for response.

answers to your questions: we may stick to windows XP to be compatible for LV 8.5.1, and because XP is mostly used in our company. yes we need to keep data to be stored for several months for data analysis of energy and power consumption and because we also need to compare data for each month to see the development and result of conserving energy in our site.  i will do study of the link you've posted first. and about the kepware OPC server, our department may not adopt a total solution from other vendor due to its cost. unfortunately, our company's 1st priority is to lower the cost . but we are trying to evaluate the DSC module eventhough of its higher cost but if truly efficient and the only one to satisfy the reliability that we need, we may adopt this.

BTW, unclebump, what do you think about using NI OPC server vs DSC module? i knew NI OPC server program development (data socket) with LV is quite easy compare to creating a new device drivers using MB library but im not sure about its disadvantages. are you aware of it?

thanks in advanced!...

[unclebump]

I've never used the NI opc server.

[Billingsley]

OPC server can't reach high update rate, ie 20 ms

[ivelson]

thanks for reminding Charles0820.

I guess our system was enough to monitor data every second so we do not need too high update rates in monitoring. what do you think other drawbacks of NI-OPC server? as far as we know, NI-OPC server was developed by NI that was highly reliable and efficient, and one of the qualified better tools (if not the best) for a system like we are planning to build.

like unclebump says before, it depends upon the system we are building. for our power monitoring system, we prioritize the cost that's why we eagerly figuring out the way to use our existing OPC server toolkit rather than DSC module (or even making LV drivers out of MB library in a worst case!). the 2nd thing is the stability of connection. now my program (create own LV drivers) suffers a lot of TCP connection error (error 56 & 60 in Modbus lib) in an unpredicted manner that's why we need to put a code for reconnection and log file subVI to trace the problem. it seems that the problem occurs always in MB ethernet receive.vi (MB lib) of different subVI's. Im still debugging this problem for 3weeks by manipulating timeouts, baudrates, etc but no success. anyway, forget the error in this forum. For the update rate, 1 second is enough.  Now we will use NI-OPC server and i'm still figuring out NI-OPC server before jumping up to DSC module.

[unclebump]

The NI OPC server looks like they have bundled kepware to me. Download the demo version of kepware and the demo of NI-OPC servers and compare them. Same two hour time limit to the demo in each. You can get 20ms update rates with the opc server and plcs. I had kepware setup in mailbox mode (unsolicited) to receive data from modicon momentum plcs configured with the I/O scanner option and ethernet ports. The plc continuously blasted data up to the computer's ethernet port and kepware would sit there listening for it. The tag engine then read the kepware data. None of the labview code had to handle any of the communication stuff. I also had the computer's ethernet port configured in a multihome setup. This gives the single ethernet port multiple ip addresses. Each plc was configured in I/O scanner to talk with a different ip address in the computer.

For your setup, an opc server is definitely the way to proceed. Once configured, all of the communication stuff happens outside of your labview code to read and display data.

You will probably want a dedicated deterministic network for this power monitoring. don't put it on the same network as all of your office pc's. Proper network design for this large of a setup will be extremely important. could even be issues with your serial/ethernet converter.

[ivelson]

thanks unclebump.

it looks like you've took a quick overview of NI-OPC server to compare it w/ kepware OPC server, greatly appreciate your time and efforts. honestly, i'm still on the 1st stage of using this NI-OPC server so after a week of studying and implementing,  i may relate with the terms you've discussed above (i.e. tag engine, I/O scanner options, mailbox mode, and maybe more!) ). anyway, we already do have the NI-OPC server and i used it once in omron PLC (data socket connection). you are right that once it is configured, the communication happens outside LV code, so i will only used the LV front panel like an HMI function to read data.

thanks for reminding the very important factor in network design setup,  i will recommend to isolate the network setup of this master from office pc's network. since i don't have experience in establishing a system like this, i am not fully aware of these factors. regarding the serial/ethernet converters, as of now we tried to monitor 2 device simulataneously and capable to get data (w/ poor connection). the MB standard says that we can make up to 247 slaves in 1 converter (am i right??) is this really true? please correct me if im wrong.

[unclebump]

Take a look at the help screen inside NI OPC server. Looks Like they forgot to update something!!