Hi,
We are using an S-series Profibus DP card and we have many types of instruments connected to it. Among others, an Optek control 4000 turbidity meter. Since this is a Profibus PA instrument, we are using a DP/PA coupler (Pepperl+Fuchs HD2-GTP-2PA) to connect to it.
Now, the problem is that the values which I am reading from the instrument seem to update only once: when Profibus communication is initiated (when rebooting the instrument, connecting/disconnecting it from the bus, changing some settings). The values on the screen of the instrument are changing, but in DeltaV once the first values arrive, they seem to be never updated. The instrument has a "freeze mode", but it is not active. I am monitoring the values from DeltaV Diagnostics.
Similar to Fieldbus, beside the value there is a status byte transmitted. During my tests its value was always 75.
Do you have any experience regarding this?
Thanks,
Istvan
Recently spent some time with Profibus PA, integrating various devices. The status for Profibus PA is very similar to the FF status parameter, with the first two bits defining BAD, Questionable, Good, so a value of 75 (01 0010 11) indicates the value is Questionable, substatus of 2, Limited constant).
Since the value is reporting Constant, then the value sent by the device is not changing.
Apart from the substatus, the PA status maps directly to the DeltaV status for the first two and last two bits. PA does not have a GoodCascade status so 128 and greater is GOOD. The last two bits are limit status, and in this case indicate Constant. Many of the Substatus values are the same as FF, but I've found a couple of extra ones (Can't find my notes at the moment.)
I've used Siematic PDM software to connect to devices with a lap top to access device configuration data.You can connect this to the PA segment and read devices while they are on line. THis might be needed to make changes to the configuration. What is possible is the Block that serves the AI value is not in the correct mode, and that is why the status is constant. The value is changing on the local display because that is fed directly by the transmitter. The PA block needs to be in Auto to actually send the value.
That's my guess.
Andre Dicaire
In reply to Andre Dicaire:
Hi Andre,
Thank you very much.
The problem was that the instrument's probe parameters were not correctly configured so the measurement was BAD.
Once instrumentation corrected that problem, I presume the function block transitioned to auto.
Now the values are being updated.