HART PROTOCOL

[wonderboutin 0]

I have a cs1 and I want to communicate with a transmeter via HART protocol can you help me ?

[Jay Anthony 118]

Is this by serial or 4-20 transmission media?

[wonderboutin 0]

By serial port.

[BobB 58]

As it is serial, you should be able to set up the protocol to communicate with the device using CX-Protocol and an on board or rack mounted serial port (SCU or SCB). I use this for Modbus RTU all the time.

[CX_Luigi 1]

apologies for resurrecting an ancient thread, but i'd like to ask if there is a way to read multiple devices through HART protocol on 4-20mA current loop. I have a batch of E+H FMP40 continuous radar levels that are polled through an CJ1W-AD081 analog card, would like to see if they can be daisy chained and their values read, both for configuration and monitoring.

[DanW 41]

As you are probably aware, HART is usually point-to-point, used for setup, configuration and troubleshooting. The ability to configure beyond the 7 or 8 generic HART commands requires a Device Descriptor file specific to the firmware/software application. So the Emerson 475 uses a DD file, Pactware uses a ___ file, Meriam uses a DOF file and Siemens uses an EDD file, non of which are cross compatible with one another. The answer to your question, "(is) there is a way to read multiple devices through HART protocol on 4-20mA current loop?" is "Yes, but probably not what you envision". a) What your analog card is missing is - ability to extract the HART signal - firmware/software to be able to read the data and do any configuration Unless your I/O card vendor supplies both of the above, you're out of luck for that card. b) A multitude of "yes, but . . ." answers: 1) There are a couple of 3rd party HART comm/I/O card vendors, with backplane cards for specific brand/model rack PLCs. I believe there's a card for A-B's controllogix. There might be others. I doubt that the cards can be used for configuration, and are only for data fetches of primary through 4th variables. Prosoft does a lot of 3rd party com cards. 2) There are several vendors of HART-to- Modbus modules. My impression is that these modules are only good for fetching primary through 4th variables, they are not for HART configuration, because of the limitation of the device descriptor file implementation. 3) HART does support multidrop operation, which fits your definition of multiple devices on a 4-20mA loop. A HART master queries the individual transmitters, each of which has a unique numeric address on the multidrop parallel daisy chained wiring loop/link. I can't recall the loop current, but it is constant, say 4 or 6mA and the HART data rides on the DC current. This involves a hardware HART multiplexor [mux] (vendors: Pepperl & Fuchs, Phoenix Contact, MTL) which to me is a de-multiplexor, which then breaks the data out into individual channels. The key is you need software: a HART master that controls the mux and knows which data to get and what to do with it. I've never run or used multidrop, but I suspect that most software fetches variables, and maybe a 2nd HART master can be put on the loop for configuration purposes, because all the configurator tools let you address devices other than the point-to-point address 0 which is typically the default. 4) Wireless HART can definitely grab variables 1-4, but configuration? I just don't know. The current versions of Wireless HART use Modbus TCP or an OPC server that uses Modbus TCP to make the data available from the gateway to a host. So this, too, is a Modbus derivative. The HART Communication Application Guide is a 175 page document which I got from the HART Foundation web site. www.hartcomm.org It covers the multidrop concept. If anyone knows anything to the contrary, I'm all ears.

[CX_Luigi 1]

thanks for your detailed answer DanW, my question started by noticing the presence of multi-point connection mode in the software I use for configuring the devices (E+H FieldCare). The HART master can configure and monitor device values so I was wondering if I could replicate its functions into PLC, allowing me to remote servicing the devices, and customer operate and/or configure them. From your reply I think the best option to explore is HART to Modbus converters, in conjunction with SCU card with a protocol macro to read values/configuring devices. By the way, am I alone in thinking that the HART masters are poorly made software pieces? I have worked extensively with two, both from Endress Hauser, ToFTool and its successor FieldCare and I found them both unwieldy, slow, complicated and generally poorly designed (for example they have different ways and file formats to save the configuration of the devices). I've tried also CX-ConfiguratorFDT, also as a DTM container like the former two, but was not able to make it communicating with the devices I use. Pactware seems the relative best of the group, but I haven't had the chance to test it deeply. I think there are huge margins of improvements for these software and probably a nice opportunity for developers to produce a decent software.

[DanW 41]

I agree that for getting HART variables the HART-to-Modbus modules are probably the easiest method. I've been impressed with the documentation from Moore Industries, I suspect that good documentation extends to their Hart-to-Modbus module, even though I haven't used one. >The HART master can configure and monitor device values so I was wondering if I could replicate its functions into PLC, allowing me to remote servicing the devices, and customer operate and/or configure them. For configuration, troubleshooting and servicing, I'd load that task onto Fieldcare or Pactware or whatever software E&H (or whomever) provides DTM's for (thanks, I couldn't remember the 3 character acronym). The point being, in the life of a field transmitter, the configuration/service part takes 0.001% of its life. For that little amount of use, using someone else's software/hardware is the only practical answer. There's no way an individual can bring the resources to bear that a manufacturer can for developing software for a limited market like instrumentation. >By the way, am I alone in thinking that the HART masters are poorly made software ? The bulk of my experience with with Siemens PDM. It tends to be reliable, but the problems are - a total lack of documentation for the specific devices - absence of specifics for using the advanced graphics associated with radar or ultrasonic level - scaling, zooming, using the baseline tool for the echo curve. It astounds me that the manufacturers can put so much effort into making a tool available and have zero resources for explaining how to best use it. Especially in today's era of Youtube video. Even if were in German, other language subtitles could convey the necessary info. For anyone looking to write code, a 'missing' software package is a scaled down, easily used database for HART diagnostics. Wireless HART has everyone pumped up about getting stranded data, including diagnostics, but what software is available to exploit the diagnostics other than Emerson's AMS at $25k?