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How can I monitor process variables of field devices?



Hello, I wanted to ask how it is possible monitoring not only the connection details such as network traffic, CPU usage etc. but also monitoring process variables of field devices in my network.

For example I have a flowmeter with Profinet interface and I'm already able to monitor its runtime, network traffic on each port etc. Now I'd like to monitor its measurings such as the flow, viscosity, pressure and so on.

I found out that SNMP could be the right way to access data of the field device using different OIDs (Object Identifier). Unfortunately, to check every OID I need the MIB file of this flowmeter that I don't have yet.

Is this the right way or do you know any alternatives to get these process variables?

Please help, thank you.

field-device flowmeter mib oid process-monitoring process-variables profinet snmp

Created on Sep 21, 2018 11:12:42 AM

3 Replies

Accepted Answer



Hello there,
we appreciate your inquiry.

Having the MIB is the optimal way to find out if there are and what the OID's for specific metrics are. It also makes it possible to use the SNMP Library sensor, which makes things easier. Our first recommendation is that you contact the device's vendor and request the MIB file.

Other alternatives include:

  • Google for relevant OID's, this can be quite productive depending on how popular your device is.
  • Use net-snmp or our SNMP Tester to walk This will ask the device for any vendor specific OIDs. Sometimes this will allow you to easily recognize relevant values and use these OIDs in PRTG. Or it will give you some OIDs to Google for.

Otherwise, there isn't much to be done. It is the vendor's responsibility to document the device's API and monitoring capabilities. If there isn't any documentation to follow it makes monitoring the device (in detail) quite difficult.

Best Regards,
Luciano Lingnau [Paessler Support]

Created on Sep 24, 2018 11:19:02 AM by  Luciano Lingnau [Paessler]



Well, finally I managed to get the MIB for my device. Now I have another problem. I did a SNMP-Walk through it and analyzed every OID the software showed me. I have to say that these OIDs are not really interesting things to monitor. There was no process variable in the OIDs, like the flow, viscosity or pressure. Usually these measurements should be in there because these are really significant. Is there maybe another way to access more information? Maybe change the community string or the port? Please help.

Created on Oct 15, 2018 9:03:06 AM



Hello pmrtb,
thank you for your reply.

Changing the ports shouldn't really bring any change, because the agent will usually just bind with one port (UDP/161) and that's it, from my personal experience I can tell you I've never seen a device where there are multiple agents listening on different ports.

As for different community names, maybe. Some devices implement security measurements where some information is only available in "Community Name A" and other metrics are available only in "Community Name B" - This would be uncommon, but not impossible.

However, please keep in mind that only the device's vendor will be able to tell for certain what is available and possible. I strongly encourage you to contact the vendor's support and ask for the MIB/OID where the aforementioned metrics (flow, viscosity or pressure) are available.

If the vendor says there are't any OID's for that, then there's not really much we can do (SNMP wise).

Best Regards,
Luciano Lingnau [Paessler Support]

Created on Oct 16, 2018 12:46:11 PM by  Luciano Lingnau [Paessler]

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