Honeywell Transmitters and DE Protocol


Thread Starter

Norm Fong

Hello I am looking for some feedback from anyone who has used Honeywell DE protocol from field transmitters, specifically to a flow computer (Omni), in preference to analog signals. What was the basis for the preference etc? My particular application is DP/P/T transmitters from orifice meter run to flow computer. Cheers
We use the Honeywell DE protocol extensively in our petroleum refinery control system. The receiving device is the Honeywell APM/HPM with the STIM I/O Processor card. The advantage of using a digital protocol to transfer the values to the control/monitoring system is that it eliminates one or more A/D and D/A conversions. The sensors of the Honeywell smart transmitter convert the pressure (ANAOLG) signal into a frequency which is then utilized by the DIGITAL processor in the transmitter to determine the appropriate value to be sent out. Using the DE protocol, the value is transferred still in the digital form for use by the receiving DIGITAL computer. There is only one A/D conversion, and that has been extensively characterized by Honeywell during the manufacturing process. If however you choose to transfer this information in a 4-20 ma form, now a D/A conversion must occur in the transmitter, and an A/D conversion must occur in the receiver to complete the transfer. Error can be introduced at each conversion, and losses can occur in the wiring between the devices. If utmost accuracy is desired, minimize the number of conversions to be made. If you are looking to do mass flow calculation, you may wish to consider one of the multi-variable transmitters by Honeywell or Rosemount. I have used the Honeywell SMV transmitters in several places, including the feeds to a sulfur recovery unit with great success. The transmitter determines dP and GP in a single housing, and will accept RTD input for the temperature. There are a number of standard calculations that the transmitter is capable of performing, including the AGA correction. Look at the Honeywell web site for the full dope. John Beck Pennzoil Quaker State Refinery Shreveport, LA