I've used GDEV quite successfully for most apps. Don't forget the STAIND output which can be used with MMAIND quite effectively to tell you whether you have a RUN>STOP>RUN state, or a STOP>RUN>STOP state. The various state conditions can be well-documented by using STATx and MMx string parameters. The only device I've been unable to automate with a single GDEV is a 3-position valve (open/partway/close) which we've used to prevent hammer when closing the valve, or any device that has 3 or more distinct positions. Brad Wilson brad.wilson@xxxxxxxxxxxxxxxx Invensys Systems, Inc 1090 King Georges Post Rd, Suite 204 Edison, NJ 08837 732-874-0087 -----Original Message----- From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On Behalf Of Corey R Clingo Sent: Wednesday, August 01, 2007 10:32 AM To: foxboro@xxxxxxxxxxxxx Subject: Re: [foxboro] "GDEV" or "VLV,MOVLV,MTR" or "CALC" - Discrete control engineering advice ? We have. Pros: --------- 1. Consistent operator interface 2. Consistent engineer interface :) 3. Good set of capabilities -- command disagreement alarming, = interlocking, output readback handling, etc. 4. Most closely resemble (but, alas, do not match in capability) the = Honeywell digital composite blocks I used pre-I/A. Cons: ---------- 1. Only 2 states. For motor starting, a third momentary state would be = nice. It causes operator confusion at times when they forget that they = have to make a RUN->STOP->RUN transition to restart a motor that was = stopped in the field. You could take care of this probably with some = logic, but we have not decided to do that yet (that has its own pros and cons). I don't think any I/A discrete control blocks have this, though, so it's not a weakness only of the GDEV. 2. I'm not sure a GDEV would do electric-actuated valves without extra = logic. There are two outputs, but I think they are always inverses of = each other or something (I can't recall ever using COUT_2). We don't have = any of these, so I can't say for certain. For our standard = air/solenoid-operated valves and motors, the GDEV works pretty well. Corey Clingo BASF Corporation "Bruley, Peter T" <Peter.T.Bruley@xxxxxxxxxxxxxx> = Sent by: foxboro-bounce@xxxxxxxxxxxxx 08/01/2007 08:57 AM Please respond to foxboro@xxxxxxxxxxxxx To "Foxboro@Freelists. Org \(E-mail\)" <foxboro@xxxxxxxxxxxxx> cc Subject [foxboro] "GDEV" or "VLV,MOVLV,MTR" or "CALC" - Discrete control = engineering advice ? We are in the process of replacing a L&N DCS with a Foxboro I/A DCS.=3D20 ------------------------------------------------------------------------ -=3D ------- We are considering using the "GDEV" block for all our open/close valves=3D20 (single coil + dual coil solenoid & motor actuated) as well as all the=3D20 motor start/stop. (instead of using blocks: VLV, MOVLV, MTR) Who out there has standardized on the "GDEV" block for on/off open/close =3D control? What have you learnt by doing this? What are the advantages? What are =3D the disadvantages? ------------------------------------------------------------------------ -=3D ------ Another method our Foxboro Engineers have recommended to us is to use =3D the "CALC" block=3D20 (instead of GDEV, VLV, MOVLV, MTR) Has anyone gone this route? What have you learnt by doing this? What are the advantages? What are =3D the disadvantages? Thank You, Peter Bruley Plant Process Computer Analyst Xcel Energy - Sherco Generating Plant Peter.T.Bruley@xxxxxxxxxxxxxx = = _______________________________________________________________________ This mailing list is neither sponsored nor endorsed by Invensys Process Systems (formerly The Foxboro Company). Use the info you obtain here at your own risks. Read http://www.thecassandraproject.org/disclaimer.html = foxboro mailing list: //www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=3Djoin to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=3Dleave = Confidentiality Notice: The information contained in this electronic message and any attachment(s) = to this message are intended for the exclusive use of the recipient(s) and = may contain confidential, privileged or proprietary information. If you are= not the intended recipient, please notify the sender immediately, delete a= ll copies of this message and any attachment(s). Any other use of the E-Mai= l by you is prohibited. _______________________________________________________________________ This mailing list is neither sponsored nor endorsed by Invensys Process Systems (formerly The Foxboro Company). Use the info you obtain here at your own risks. Read http://www.thecassandraproject.org/disclaimer.html foxboro mailing list: //www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave