11/19/2011 2:19 PM | |
Joined: 9/27/2006 Last visit: 9/22/2024 Posts: 12282 Rating: (2685) |
Hello elango; You say your meter has a RS-485 port, that is a good start, the S7-200 ports are also RS-485. But you must make sure that the meter is enabled (by the manufacturer) as a Modbus RTU slave, if you want to exchange data with the S7-200. The often used analogy is that you and I could connect over a telephone line, but that if you do not know English we might have a lot of trouble communicating, as I do not understand Hindi... So both partners must be able to connect electrically (RS-485 in this case) but they must also speak the same language. If you can validate that the meter meets this requirement, then there is an add-on library for Modbus RTU available in the S7-200 family. You will find variours FAQs discussing this issue in the following link, and the S7-200 System manual will describe the Modbus instructions to be implemented in your program: https://support.automation.siemens.com/WW/llisapi.dll?query=S7-200+modbus+library&func=cslib.cssearch&content=adsearch%2Fadsearch.aspx%3Ftab%3D2&lang=en&siteid=csius&objaction=cssearch&searchinprim=_searchinprim_&nodeid=99&x=16&y=8&cssearchengine=NEW&x=0&y=0 S7-200 System Manual Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 11/19/2011 2:21 PM |
|
11/21/2011 9:44 AM | |
Posts: 5 Rating: (0) |
Thanks for your kind attn.
Sir I have attached Slave equipment meter manual. In this manual I noted This meter is RS485 (half duplex) Baud rate - 9600 parity - none stat bit - 1 stop bit -1 RS485 interface - MODBUS Protocol In RTU MODE. The meter can be used as slave. You can find the meter manual in pdf format in attachment. Thanks Elango AttachmentQUASAR 190507.pdf (256 Downloads) |
Last edited by: sivaelango at: 11/21/2011 9:51 AMLast edited by: O_Moderator at: 11/21/2011 9:50 AMmanual transferred to attachment |
|
11/21/2011 3:52 PM | |
Joined: 1/17/2007 Last visit: 8/21/2024 Posts: 1545 Rating: (537) |
The Siemens system should have no issues communicating with the meter, as it uses standard modbus RTU protocol. You will be wanting to use function codes 3 (read holding registers) to read the data at addresses 40001 on-wards and function code 4 (read input registers) to read data at addresses 30001 to 39998. A few pointers to bear in mind. 1) The S7 modbus software requires an offset instead of an address. The offset is calculated by subtracting the data type base address from the required address. So to read holding register address 40101 the offset would be 40101 - 40001 = 100. The same calculation applies for input registers, but with the 40001 replaced with 30001 (e.g. 30201 - 30001 = 200). 2) The slave will need setting up with a unique slave address. If you have more than one meter on the same network, each will need a unique address. The S7 modbus software is then configured to poll the required slave address for data. I do not have an example project for you to study, but I am sure that someone on here will have. This thread may help. |
Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. |
|
This contribution was helpful to1 thankful Users |
Follow us on