labview communication to Hart equipment using serial interface

[showme]

I am trying to communicate with various Fluke / Hart temperature equipment (Chubb E4, 9107 Dry well..) with LabView 8.0 thru the serial interface. I have the list of commands from Hart but they are not the same as the typical serial write / read commands and are not working. I am communicating to other equipment using the serial interface with normal serial command formats (i.e.  001c000000FABD, etc... ) but Hart commands are single letters (i.e.   t<CR> )   for reading the temperature. I'm not sure if the problem is with Hart or LabView VIs that I am using.
Thanks in advance

[RavensFan]

How are you connecting to the Hart devices?  Are they RS-232, RS-485, something else?  Is it through a PC, real-time OS PC, or fieldpoint, or something else? 

It's probably not the LabVIEW VI's.  LabVIEW will just send out whatever characters you tell it, whether it is a stream of Hexadecimal bytes or string charachters (which of course are hex bytes by way of the ASCII table.)

Check your hardware interface, and your protocol settings and baud rate.  Hart usually requires special hardware devices because my understanding is that it is a serial communication protocol placed on top of a 4-20 mA analog signal.  So it's not really RS-232 or RS-485.  So the question comes down to what interface hardware you're using and what kind of drivers it supplies.

[showme]

Thank you for the post, Raven Fan. I'm sorry, I didn't communicate clearly. I know about the 4-20mA loop 'Hart' protocol but I'm not using it. This equipment is made by Hart Scientific / Fluke.This is a simple USB to RS232 cable that connects my PC with the Hart Scientific 9107 Temperature Dry Well RS232 jack. I'm using NI written LabView VIs to talk to other serial devices using the old clunky 13 ASCII character string and it works fine. But when I try using the same VIs using Hart Scientific's more "simple" command set it doesn't talk. Its going from the old 13 character string to a 1 or 2 character string. I'm wondering if LabView's VIs are feeding the newer information in the old format or something like that.  Any suggestions?
Thanks in advance.

[RavensFan]

I'm sorry.  I was the one who jumped to the conclusion that it was Hart protocol.

You are using in USB/RS-232 converter.  I assume you see this as another Com port on your computer.  I've used these devices before without problems, those a few people on the forums have said that certain brands just haven't worked for them.

As I said before, double check all the baud and parity settings.  Double check that you have the right cable, whether it need to be null modem or a straight through cable.

The manual  ftp://ftp.hartscientific.com/manuals/9105-07.pdf looks like it should be a null modem cable.

Check that  you are actually sending out a CR character at the end of your string.  Do you need to send a capital T or a lower case t.  That actually messed me up for a few minutes recently on a device I was trying to communicate with.   t<CR> should look like t\r if the constant you are writing is set to \codes display or 74 0D (lower case t) or 540D (upper case T).

Is the device set up to return a line feed in its response?  Have you provide enough of a delay between the VISA write and read to give the instrument time to send the response?

Try things in hyperterminal.  It is a simple place to start to see if you have basic communication there.  If you do, then you can focus on the LabVIEW.  If you don't, then you know the issue is with the wiring, device, or Windows driver or settings.

Are you using the basic LabVIEW VI's for Serial Read and Write or VI's that from somewhere else?  You said "I'm wondering if LabView's VIs are feeding the newer information in the old format or something like that."  LabVIEW is only going to send out whatever you tell it to send out. 

Sorry it's a bunch of questions rather than answers, but hopefully it gets you looking in different areas that you may not have thought of.

[JGanhao]

What HART modem are you using?

[JGanhao]

What HART modem are you using?

[johnsold]

"showme" has not logged into the Forums since 2008. Please start a new thread with complete information about your problem.

Lynn