HART transmitter we can simulate 4 to 20 ma with HART communicator. what about foundation fieldbus instruments? how we can simulate with communicator to dcs 0 to 100% without process variables?
> HART transmitter we can simulate 4 to 20 ma with HART communicator. what about
> foundation fieldbus instruments? how we can simulate with communicator to dcs 0
> to 100% without process variables?
Why do you need to simulate with a handheld when you can do it from the control room with fieldbus using your DCS?
That said, most of the major DCS suppliers support simulation with FOUNDATION fieldbus. ABB, Emerson, Smar, and most others.
I am not sure if the current version of the Emerson 475 supports fieldbus simulation, but again I am not sure how relevant a question this is. You can change device parameters using a 475, you can do device diagnostics, but why would you run simulation for a single fieldbus device using a handheld communicator? Fieldbus devices are perfectly capable of indicating their own health and will let you know immediately if there is a problem with the device. Simulation to me would only make sense if you were doing some kind of what if analysis, which would require a view of the behavior of the overall control system anyway.
At a local ISA meeting about a year ago, I sat through a typical power point slide presentation on the benefits of FF, all aimed at reduced wiring costs. OK.
Since I have to keep things running in the plant, I naively asked the same question as the OP and got the same brush-off, "I don't know but trust me, FF is wonderful and will never let you down". Uh-huh.
I don't know why the OP asked the question but a loop check is a standard practice in the analog 4-20mA HART world to verify loop functionality. It would be nice to know how the same thing is accomplished in FF, even if the most wonderful comprehensive all-encompassing diagnostics are available somewhere, interpretable by someone with a Captain Midnight decoder ring.
Ironically, someone on LinkedIn recently asked the same question, and because I don't know how restricted LinkedIn is, I copied the question and the answer and pasted them below to blow away some of the smoke around this arcane and esoteric issue.
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Question: I was wondering if you are able to simulate in Foundation Fieldbus ? I do not see it in the Transducer Block menu on the 475? can anyone help?
Answer: There's a "simulate" value and enable bit (?) in the input blocks, like an AI for example. We don't use it very much. You can also put AI's in "Manual" mode, where you can set the output and status to whatever you please. Unless - you set the option bit "Uncertain if Manual Mode" . . . you can still make the output whatever you want, but the status can't be set to "good".
I can see a few reasons to use the AI's MAN mode instead of Simulate. For one, I can set the output in the engineering units I've configured for the host. Seems to me the "simulate" value is in units of XD_Scalce or Field_val_percent (?) - and may not be linearized i.e. the output may be the square root of your "simulate" input if that's what you've selected for linearization.\
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It might not be a comprehensive answer, but it's a start.
Seems that simulation is a complicated solution to a simple problem. You asked about the Foundation Fieldbus equivalent to a loop check. The simulation answer was to a different question.
Loop check: each Foundation Fieldbus instrument is given a factory ID that is used during the initial configuration to install the tag name and the strategy data. When you do the configuration, you will be doing a loop check. It is not done by the installation tech like 4-20ma, it is done at the maintenance console as part of installation. All that is required is that the Foundation Fieldbus instrument be connected to either an HSE Linking Device or to an H1 interface card in the DCS.
The FF AI function block contains a SIMULATE parameter. There you can simulate the PV value and status. That is, you can even simulate sensor failure and see the system responds correctly.
However, note that 0/25/50/75/100% loop test is not done for FOUNDATION fieldbus or other digital communication since digital signals are inherently not subject to non-linearity and other distortion associated with analog signals.
A 4-20 mA signal can be limited (e.g. at 18 mA) due to resistance/voltage, biased due to ground loop, or become non-linear due to signal converters and safety barriers etc. Therefore 5-point loop test has to be done for 4-20 mA. However, this does not happen for a digital signal. If the value is 123.45 in the transmitter it will be received as 123.45 in the system. This is why 5-point test is not done for FF.
There are four principal reasons why a 5-point loop check has to be done for devices using a 4-20 mA signal:
. Check the device is connected to correct IO card terminal
. Detect range mismatch
. Detect current calibration mismatch
. Detect non-linear or limiting element in current loop
The four corresponding points for FOUNDATION fieldbus (FF): . If the Fieldbus device is connected to the wrong bus or interface card terminal, it will appear in another "live list" so you know it is connected wrongly. If connected to the correct terminal/bus, the system will automatically bind it to its database tag. The device is displayed in the live list with tag, manufacturer, device type, unique ID, version, and other pertinent information so you can uniquely identify it in many ways without simulating the signal
. Fieldbus transmitters don't use range. The value is transmitted digitally in engineering unit so there is no range mismatch
. Fieldbus devices do not have analog output and the system interface card has no analog input so there can be no current calibration mismatch
. Fieldbus devices use digital communication. It does not get distorted, non-linear, limited, or offset etc. If bits are distorted, this is detected by the communication error checking
However, if you want to simulate the PV to test your control strategy (direct/reverse action), alarm trips, response to failures, display in face plates, graphics, and historian etc. simulation is indeed possible. It is done from the AI function block (not from the transducer block).
If you could post the link to the Linkedin posting I would be grateful. I'd like to jump into the conversation to clarify
> Usually devices have a hardware protection jumper that you need to set
> to enable simulation before you can simulate from the SIMULATE parameter
Last time I helped commission a plant in China one brand of transmitter (I think Rosemount) had the Simulate Enable jumper and we could simulate from the console. But a different brand (I think E&H), didn't have the jumper and the only way we could simulate was by getting the tech to use his field calibrator which made the process painfully slow.
I'm back over there next month to commission another plant, I will take better note.
Try reading a manual in Mandarin and working through a translator, that's fun.
I have also faced the similar problem in Rosemount 5300 Level transmitter. The simulation jumper is not available. Even the simulation option is not available in AI function block.
