We have a flowmeter with 4-20 mA output. Is it possible to use a converter to change the analog output to fieldbus foundation? If so ok, anybody can give us a brand name?
Some people use the Rosemount 848T. It is an 8-input Mux that will accept a variety of analog signals. You could also use one of their temperature transmitters in "millivolt" mode; choose your own dropping resistor to get a workable range. We use the 3144 but they have a
cheaper "puck" type that might work (not sure if it does millivolts) - I think it's a "648".
Smar makes a product also but I don't know the model nor have I used it.
There may be converters commercially available but I've not heard of any. In my experience the service technicians I work with have to replace the entire transmitter electronics to convert a unit from 4-20mA to Foundation Fieldbus.
It should be remembered that Foundation Fieldbus utilises a Digital signal to communicate (in some cases) a huge amount of data from/to a device, whereas a 4-20mA signal is only able to communicate one value. If a converter exists I fail to see how this would advantage you (with the exception of reduced wiring) as you wouldn't be able to realise one of the major advantages of Foundation Fieldbus, this being the access to other available information within the transmitter.
After sending my last post I discovered from a colleague that SMAR offers a current to Foundation Fieldbus converter Model: IF302 (there is also a unit that converts to Profibus-PA Model: IF303 for those that are interested). The SMAR website appeared to describe these converters as a one-to-one type device, but I've been assured you can get multiplexor types as well.
> We have a flowmeter with 4-20 mA output. Is it possible to
> use a converter to change the analog output to fieldbus
> foundation? If so ok, anybody can give us a brand name?
Does it mean that any normal instrument can be transferred to FF instrument through CURRENT/FF converter? How regular FF instruments works,do them need current/FF converter?
The SMAR converter previously mentioned is a 3-channel device. It takes up to 3 different 4-20mA analog signals and converts them to Foundation Fieldbus H1. Each channel can be configured with all of the function blocks appropriate for an AI device. The AI block takes care of linearization, smoothing, and limit alerts. You can even do cascade control if for example one input is the output of a heat exchanger, and another is the flow rate of steam for that heat exchanger. This would require two PID blocks to be instantiated in this device. The output from the SMAR IF302 is one FF H1 link that must be wired to a FF H1 termination on an FF I/O card. The PV of all 3 AI blocks, all PID attributes and status, and any other configured blocks are accessible via this one wire pair. While the IF302 is a great device, it does not access any HART data on the analog instruments.
> We have a flowmeter with 4-20 mA output. Is it possible to
> use a converter to change the analog output to fieldbus
> foundation? If so ok, anybody can give us a brand name?
