FBM1, HART 275 and Rosemont 3051 Transmitter
Our instrument guys are having trouble communicating with a HART 275 communicator to a Rosemont 3051 level transmitter while connected to the Foxboro I/A FBM1 input point. The instrument is being loop powered by the FBM1 (P and P+). The only way we can get it to communicate is to put a 250 ohm resistor across the pair of wires (parallel). This allows us to communicate with the transmitter but we will not want to do this will the instrument is in service. I have tried this with several different HART 275s, FBM1s and 3051 level transmitters. If we disconnect the loop from I/A and use an Altec to power the loop, everything works as it should. This eliminates our cabling as a problem, in my humble opinion. Has anyone else experienced this problem? Is there a solution to allow the communicator to work without a resistor across the pair of wires? Rory Loupe The Dow Chemical Company LHC-3 P.O. Box 150, Building 6801 21255 highway 1, Building 6801 Plaquemine, LA 70765-0150 USA Plaquemine, LA 70764 USA Phone: 225.353-6409 Fax: 225.353.6968 E-mail: [EMAIL PROTECTED] --- This list is neither sponsored nor endorsed by the Foxboro Company. All postings from this list are the work of list subscribers and no warranty is made or implied as to the accuracy of any information disseminated through this medium. By subscribing to this list you agree to hold the list sponsor(s) blameless for any and all mishaps which might occur due to your application of information received from this mailing list. To be removed from this list, send mail to [EMAIL PROTECTED] with unsubscribe foxboro in the Subject. Or, send any mail to [EMAIL PROTECTED]
RE: FBM1, HART 275 and Rosemont 3051 Transmitter
We have and continue to experience this. We are having to go as high as 500 Ohms because of the low resistance in the FBMs. Our instrument guys connect the HART communicator across the resistor which is hooked in series not parallel. We found some terminal strips (from Phoenix Contact I believe) that have modular resistor inserts to avoid having to splice resistors inline. Rosemount states that at least 250 Ohms of loop resistance is required for the HART communicator to communicate to the smart transmitters. I believe they were assuming a certain amount of resistance at the input modules when they stated that also. Maybe some other DCS's have higher input resistance and it is not a problem. Foxboro's is pretty low. Chad Airhart Senior Instrument, Electrical Control Systems Engineer Equistar Chemicals, LP. Victoria, TX Wk. (361) 572-2568 Pgr. (361) 270-2214 alpha messaging at [EMAIL PROTECTED] Fx. (361) 572-2541 -Original Message- From: Loupe, Rory (RJ) [SMTP:[EMAIL PROTECTED]] Sent: Thursday, August 30, 2001 10:52 AM To: '[EMAIL PROTECTED]' Subject: FBM1, HART 275 and Rosemont 3051 Transmitter Our instrument guys are having trouble communicating with a HART 275 communicator to a Rosemont 3051 level transmitter while connected to the Foxboro I/A FBM1 input point. The instrument is being loop powered by the FBM1 (P and P+). The only way we can get it to communicate is to put a 250 ohm resistor across the pair of wires (parallel). This allows us to communicate with the transmitter but we will not want to do this will the instrument is in service. I have tried this with several different HART 275s, FBM1s and 3051 level transmitters. If we disconnect the loop from I/A and use an Altec to power the loop, everything works as it should. This eliminates our cabling as a problem, in my humble opinion. Has anyone else experienced this problem? Is there a solution to allow the communicator to work without a resistor across the pair of wires? Rory Loupe The Dow Chemical Company LHC-3 P.O. Box 150, Building 6801 21255 highway 1, Building 6801 Plaquemine, LA 70765-0150 USA Plaquemine, LA 70764 USA Phone: 225.353-6409 Fax: 225.353.6968 E-mail: [EMAIL PROTECTED] --- This list is neither sponsored nor endorsed by the Foxboro Company. All postings from this list are the work of list subscribers and no warranty is made or implied as to the accuracy of any information disseminated through this medium. By subscribing to this list you agree to hold the list sponsor(s) blameless for any and all mishaps which might occur due to your application of information received from this mailing list. To be removed from this list, send mail to [EMAIL PROTECTED] with unsubscribe foxboro in the Subject. Or, send any mail to [EMAIL PROTECTED] --- This list is neither sponsored nor endorsed by the Foxboro Company. All postings from this list are the work of list subscribers and no warranty is made or implied as to the accuracy of any information disseminated through this medium. By subscribing to this list you agree to hold the list sponsor(s) blameless for any and all mishaps which might occur due to your application of information received from this mailing list. To be removed from this list, send mail to [EMAIL PROTECTED] with unsubscribe foxboro in the Subject. Or, send any mail to [EMAIL PROTECTED]
RE: FBM1, HART 275 and Rosemont 3051 Transmitter
We have had this problem as well. As Chad said, it exists because the dropping resistor on Foxboro FBMs is 50 ohms, which does not give enough loop resistance for the HART handheld to read the superimposed digital signal. I do not believe Foxboro offers a 250-ohm dropping resistor option (I asked once) on the classic (100-series) FBMs. I hope they do on the 200-series. Every other system I've runn across (Allen-Bradley, Triconex, Honeywell) use 250-ohm resistors. Corey Clingo Sr. Engineer BASF Corporation Airhart, Chad M. [EMAIL PROTECTED] on 08/30/2001 11:00:01 AM Please respond to Foxboro DCS Mail List [EMAIL PROTECTED] To: 'Foxboro DCS Mail List' Foxboro cc: Subject: RE: FBM1, HART 275 and Rosemont 3051 Transmitter We have and continue to experience this. We are having to go as high as 500 Ohms because of the low resistance in the FBMs. Our instrument guys connect the HART communicator across the resistor which is hooked in series not parallel. We found some terminal strips (from Phoenix Contact I believe) that have modular resistor inserts to avoid having to splice resistors inline. Rosemount states that at least 250 Ohms of loop resistance is required for the HART communicator to communicate to the smart transmitters. I believe they were assuming a certain amount of resistance at the input modules when they stated that also. Maybe some other DCS's have higher input resistance and it is not a problem. Foxboro's is pretty low. Chad Airhart Senior Instrument, Electrical Control Systems Engineer Equistar Chemicals, LP. Victoria, TX Wk. (361) 572-2568 Pgr. (361) 270-2214 alpha messaging at [EMAIL PROTECTED] Fx. (361) 572-2541 -Original Message- From: Loupe, Rory (RJ) [SMTP:[EMAIL PROTECTED]] Sent: Thursday, August 30, 2001 10:52 AM To: '[EMAIL PROTECTED]' Subject: FBM1, HART 275 and Rosemont 3051 Transmitter Our instrument guys are having trouble communicating with a HART 275 communicator to a Rosemont 3051 level transmitter while connected to the Foxboro I/A FBM1 input point. The instrument is being loop powered by the FBM1 (P and P+). The only way we can get it to communicate is to put a 250 ohm resistor across the pair of wires (parallel). This allows us to communicate with the transmitter but we will not want to do this will the instrument is in service. I have tried this with several different HART 275s, FBM1s and 3051 level transmitters. If we disconnect the loop from I/A and use an Altec to power the loop, everything works as it should. This eliminates our cabling as a problem, in my humble opinion. Has anyone else experienced this problem? Is there a solution to allow the communicator to work without a resistor across the pair of wires? Rory Loupe The Dow Chemical Company LHC-3 P.O. Box 150, Building 6801 21255 highway 1, Building 6801 Plaquemine, LA 70765-0150 USA Plaquemine, LA 70764 USA Phone: 225.353-6409 Fax: 225.353.6968 E-mail: [EMAIL PROTECTED] --- This list is neither sponsored nor endorsed by the Foxboro Company. All postings from this list are the work of list subscribers and no warranty is made or implied as to the accuracy of any information disseminated through this medium. By subscribing to this list you agree to hold the list sponsor(s) blameless for any and all mishaps which might occur due to your application of information received from this mailing list. To be removed from this list, send mail to [EMAIL PROTECTED] with unsubscribe foxboro in the Subject. Or, send any mail to [EMAIL PROTECTED] --- This list is neither sponsored nor endorsed by the Foxboro Company. All postings from this list are the work of list subscribers and no warranty is made or implied as to the accuracy of any information disseminated through this medium. By subscribing to this list you agree to hold the list sponsor(s) blameless for any and all mishaps which might occur due to your application of information received from this mailing list. To be removed from this list, send mail to [EMAIL PROTECTED] with unsubscribe foxboro in the Subject. Or, send any mail to [EMAIL PROTECTED] --- This list is neither sponsored nor endorsed by the Foxboro Company. All postings from this list are the work of list subscribers and no warranty is made or implied as to the accuracy of any information disseminated through this medium. By subscribing to this list you agree to hold the list sponsor(s) blameless for any and all mishaps which might occur due to your application of information received from this mailing list. To be removed from this list, send mail to [EMAIL PROTECTED] with unsubscribe foxboro in the Subject. Or, send any
