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HART vs. MODBUS RTU

12/11/2009 3:40 AM

can we use HART instead of MODBUS RTU & viceversa?

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Guru
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#1

Re: HART vs MODBUS RTU

12/11/2009 4:00 AM

HART is a communications protocol that is superimposed on top of an analog 4-20mA signal and is transparent to the receiving analog instrument. Does that help?

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Anonymous Poster
#2

Re: HART vs MODBUS RTU

12/11/2009 10:56 AM

HART or Highway Addressible Remote Transducer protocol uses a superimposed 1200 or 2200 Hz

signal on a 4-20Ma output or a DCV input (depending on the configuration of the device). This signal has no effect on the operation of the device. These "pulses" represent the zeros and ones in the communication. Most HART capable devices are already configured with the necessary variables available for change to suit your application. Google "HART Communicator". MODBUS on the other hand is a dedicated serial protocol typically using CAT5 and RJ45 cables and plugs and communicates with bytes of info. I think the answer to your Q is how is your hardware configured.

P.S. Check HART FOUNDATION for tutorials. I'll keep an eye out if I can help more. RDGRNR

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Anonymous Poster
#3
In reply to #2

Re: HART vs MODBUS RTU

12/12/2009 4:27 AM

Dear sir

i have to configure a Modbus protocol which is communicating with a hart modem to SCADA.

From where i can get the confiquration steps and commissioning steps

Thank you for your help

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Guru
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#9
In reply to #3

Re: HART vs MODBUS RTU

09/25/2024 3:17 AM

Well, if it doesn't say in the instructions for the <...hart modem...> or the <...RTU...> then the next step would be to make telephone calls to the vendors' technical helplines, and ask the questions there. One might also ask:

  • What guidance is available from the origin of the <...have to...>?
  • Is there a Mentor at the facility that can help?
  • What precedent has been set among other installations?
  • Is there a facility-specific Standard Practice protocol that could be followed?

With the vendors' names and the equipment part numbers still being withheld from the forum, that's about as far as it can go.

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Power-User

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#4

Re: HART vs. MODBUS RTU

12/12/2009 8:33 PM

It is very unlikely that you will be able to run Modbus RTU and HART on the same serial port.

You mentioned a HART modem. So I have to assume that you are not using point-to-point HART, but that you are using HART multidrop, with multiple HART field devices connected to a HART multiplexor (MUX) module. HART MUX modules typically talk to the PC SCADA software over an RS-232 port (the physical link could be a phone modem or RS-485 conversion for distance's sake, but on the PC side communications are typically RS-232 on a COM port).

I also assume that your effort is an attempt to run the same SCADA/HMI software for both HART and Modbus on the same PC. Is that the case?

Modbus is so widespread that most SCADA/HMI products have a generic Modbus RTU (serial) driver. But that's not a guarantee. Does your SCADA have a Modbus RTU driver?

Most field instruments do not have Modbus, whereas most have HART. So I assume that you want to keep the HART and add Modbus for some additional device(s). Is that the case?

If so, your problem will be the availability of the serial port to the application(s). Given my experience in the Windows O/S world with HMI/SCADA software, I would not consider attempting to mix both HART and Modbus protocols on the same serial port. Too complex. I would begin by obtaining and installing a second serial port for the PC. If you're running some other O/S, your experience might differ.

With HART on one serial port and Modbus RTU on a different serial port, assuming your SCADA supports such, then your SCADA is likely to be able to handle both protocols.

Configuration details are in the SCADA documentation.

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Anonymous Poster
#5
In reply to #4

Re: HART vs. MODBUS RTU

12/12/2009 11:12 PM

Dear Sir

We are using MODBUS with RTU driver and multidrop HART system for Field instruments. We have SLC-5 (Allen bradly) which is interfaced with field instruments.

SLC-5 communicates through controlnet to the MODBUS driver which is connected to Customer host computer.

i would like to ask you any converter is required for controlnet to interface with Modbus RTU driver.

Thanks

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Guru
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#7
In reply to #5

Re: HART vs. MODBUS RTU

12/14/2009 3:31 AM

How about Allen Bradley's local technical support telephone helpline?

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Power-User

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#6

Re: HART vs. MODBUS RTU

12/13/2009 2:52 PM

> SLC-5 communicates through controlnet to the MODBUS driver which is connected to Customer host computer.

I assume you mean that your SCADA application has a Modbus (master) driver on the host PC computer.

1) One option is to put a backplane Modbus card into the SLC, like a Prosoft Modbus card. The Prosoft cards can be Modbus master or slave, but most HMI expect to be a master, by default.

Prosoft is Allen Bradley's certified partner and are truly experts in what they do.

Using Modbus in this manner would not use the SLC's ControlNet in any fashion.

If you opt to use ControlNet is some fashion then, yes, you will need a box that is both a protocol and physical link layer converter gateway.

Google might find others.

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Anonymous Poster
#8

Re: HART vs. MODBUS RTU

02/09/2010 7:05 AM

Hi!

Here you are the website of a product of my company:

http://hartmodbus.giemdp.com.ar/

This product is a HART to Modbus Protocol Converter, it allows the connection of smart field instruments that use HART protocol over 4-20mA to monitor and control equipments that use Modbus RTU protocol.

Also the device can be used as a HART modem to configure a HART device using a PC or Laptop.

I'm working in GIE S.A, a company company dedicated to the integrity of Oil and Gas facilities. Its main office is located at Mar del Plata (Buenos Aires, Argentina). Our website is:http://www.giemdp.com.ar

For any query, please contact Us.

Best Regards.

Eng. Alejandro Uriz

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