Emerson Exchange 365

DeltaV Serial Communication to Computrac Moisture Analyzer

I would like to get the moisture results from my Computrac MAX 5000 moisture analyzer into DeltaV.  The user manual says that it can communicate over a serial connection (and provides baud rate, stop bits, parity, etc) but does not specify anything further.  Does anyone have any experience doing this (or something close to it)? 

• serial
• Computrac

jasonbum

• 22 May 2015 2:53 PM
• Cancel

6 Replies

• Ray Emerson

  

  • 22 May 2015 3:11 PM

  Jason -
  Do you have any documentation from the manufacturer on what the device actually "speaks"? That's been my biggest hurdle in similar projects, since "serial" is so generic a term. I see it's an RS-232 physical setup, but nothing about its being MODBUS RTU or ASCII for the communications protocol.
  
  Based on the manual, the device SEEMS to publish data (rather than requiring it be polled from a program like HyperTerminal), which is good. What I'm not seeing is (1) How to set a MODBUS address for the device and (2) What the dataset breakdown is.
  
  #2 can be resolved through trial and error. #1 is a little trickier, as the DeltaV Serial card does require that each device on the bus have a unique address.
  
  I'd recommend a call to AZI and ask if they have a communications manual, or any more detail for connecting this to a MODBUS network. AZI may have purchased a communications board from another vendor, rather than develop their own, so you might also ask if they can point you to that other company, in search of additional information.

  • Cancel
• DBacker

  

  • 22 May 2015 7:39 PM

  Setting up Serial Communications has 2 major parts: 1 - configuring the port on the serial card to communicate with the other device and 2 - configuring the datasets under the Port for transferring the data.
  
  I'm presuming the serial protocol is MODBUS RTU because I've done a bunch of serial cards and they have all be MODBUS RTU. It's a pretty safe bet. Typically the DeltaV Serial card is the MODBUS master.
  
  You need to know the MODBUS slave addresss (or know how to set it to what you want the slave address to be), whether the communication is half duplex or full duplex, baud rate, stop bits, parity. From here you know how to set up the port on the DeltaV serial card to get it to communciate with the moisture analyser. You might be able to grope around with defaults and get this working.
  
  In order to setup the data sets, you need to know which data are in which modbus register addresses. Frequently discrete data (groups of alarm bits or status bits are accessed as MODBUS "coils"). Integer or floating point data can be in Modbus "input registers" (30000 addresses). Integer or floating point data can also be in MODUBUS "holding registers" (40000 addresses).

  • Cancel
• jasonbum

  

  • 26 May 2015 4:21 PM

  In reply to Ray Emerson:

  I was able to read what the scale is sending out through Hyperterminal using the serial settings recommended by the vendor. I am looking at getting a converter device that will allow me to take the ASCII info and map it to Modbus registers so it can be communicated through the DeltaV serial card. I was hoping to go directly from the scale to DeltaV, but that does not seem like a possibility right now.

  • Cancel
• Ray Emerson

  

  • 26 May 2015 4:55 PM

  In reply to jasonbum:

  Hi, Jason.
  The DeltaV Serial Card (VE4006P2 / SE4006P2) can handle ASCII at the port level. String manipulation may be a little tricky, but you can certainly take the raw ASCII in without intermediate devices. This might be worth a shot.
  
  In the odd case where you DO need an intermediate device (typically only necessary when the device requires an external poll to output, instead of a periodic-broadcast device), I've used some really great tools from Chessel. Their engineers do the mapping for you, and it's a very robust solution. I've used these in many applications involving equipment with a Serial port, but non-standard protocol.

  • Cancel
• jasonbum

  

  • 25 Sep 2015 6:24 PM

  In reply to Ray Emerson:

  I have been able to connect the moisture meter to a device (460MMA from RTA Automation) that takes the ASCII message and parses it out into fields that are sent out from the Modbus RTU master device (460MMA) to the Modbus RTU slave device (DeltaV serial card). I am able to receive ASCII messages from the meter and parse then into three fields: two that are strings and one that is a floating point. I am able to read the floating point data fine on the DeltaV side. The string data does not appear to be coming through. Am I missing something here on string data being sent to the DeltaV serial card? The two strings appear to be correct from the 460MMA side. The datasets that are string w/ status types do not appear to be getting any data. Any thoughts?

  • Cancel
• jasonbum

  

  • 29 Sep 2015 7:42 PM

  In reply to DBacker:

  Did you have any luck with string data? I can get the floating point data to work but not the strings.

  • Cancel