CitectSCADA and Mitsubishi digital devices

[lou80 0]

Can someone out there help me ... I've configured a project in CitectSCADA to collect production data from 7 FX2C Mitsubishi PLC's. To count production I'm using the digital device X23. This device turns on each time a product is fabricated. The problem is that this device doesn't turn on/off with the same frequency in CitectSCADA as it does in GX- developer. Sometimes it doesn't even turn on in Citect. Also not all digital tags in Citect seem to be working properly. What could be the problem?

[thomas1000 0]

Hi, I had similar problems a few weeks ago with a flowmeter totaliser. I resolved the problem by allowing the PLC to increment the totaliser count and allowing the SCADA to view the totaliser from the PLC register. Hope this helps. Edited 3 Jul 2006 by thomas1000

[Colin Carpenter 10]

It's down to the time delays involved in the comms between the SCADA software and the PLC. Sometimes when it looks, it's on, sometimes it's not. It's surprising that even Developer is showing a regular pulse. As stated, use a counter or incremented data register to count the pulses and then read the register. Much better option. The Rule .... when using a PLC to count pulses (not hi speed counters), as long as the pulse duration is greater than the PLC cycle scan time, then you will catch all the pulses. If the pulse duration is less than the PLC cycle scan time, then you are gonna miss some of them ..... how many you miss depends on the difference between the pulse duration and the scan time.

[lou80 0]

[panic mode 246]

what is the frequency? HMI will allways have updates. Don't know about your package but I've seen few times that some products (standard HMIs) do not even report comm error or timeout if specified update time (refresh) is not long enough. They simply stop reading rest of the tags and start from begin as dictated by refresh setting. Increasing refresh time will mean slower updates but more tags will be updated.

[FNMdeJong 7]

Every scada package will block the communication. So if one tag (bit) is requested the driver will request at least 16 bits. In Citect this is also the case. So if you have 1 tag, every request is the same tag. if you have 2 tags lets say for instance X0 and M0, there are 2 requests needed to get the information. So the refresh frequency is half the time when requesting 1 tag. When using citect you can try to lower the refresh time of you're screens to get a better indication of the counter. You can also adjust the driver properties, like block size, retry's and so on. There are some whitepapers available on this kind of topics on the Citect webpage.

[lou80 0]

I've worked on my update time, but no succes. Another explanation I got is that maybe my digital tag X23 doesn't stay on long enough for Citect to catch it or that maybe when Citect polls this variabele, it has just jumped back from 1 to 0, so Citect will not be able to catch all 0 to 1 transitions. What is your response to this explanation? (Every time that X23 changes from 0 to 1, it stays at value 1 for about 1 sec)

[waynes 8]

lou80, use a counter inside the plc. It is never a good idea to use the scada as a counter. What will happen if your communication goes down or the SCADA PC needs to be restarted? You will loose all production counters during this period. Use a counter or register inside the plc, example: D0 or C0. Read the counter/ register value and do what you need to.