10/1/2021 6:51 AM  
Joined: 4/28/2015 Last visit: 10/2/2021 Posts: 2 Rating: (0) 
Good day to all, I have a SITRANS P DS III Measuring transducer for differential pressure with MLFB 7MF44331EA221AB7Z with options Y01+Y21. The situation that I have is: After changing the mode of operation MODE 11 from "Lin" to "SrLin" (because I want to see the flow on output 4...20 mA) and changing back from "SrLin" to "Lin" I have a problem with adjusting of the values of the Parameter 2, 3, 5 and 6. Meaning: During operation MODE 11 = "Lin", Parameter 5 was 0 mbar and Parameter 6 was 600 mbar. Parameter 2 was 0 mA and Parameter 3 was 20 mA. After changing from "SrLin" to "Lin" I no longer can increase the Parameter 3 to 20 mA, instead, the Parameter 3 is somehow locked, will not go up or down. What I am seeing are some new values for Parameter 5 and 6. After adjusting them to 0 mbar and 600 mbar again, the values of Parameter 2 and 3 are set to i.e. 4,2 mA. Parameter 3 I cannot move up/down. but Parameter 2 I can increase and decrease. I believe the problem is in sequence of operation or it can be problem with units (I have tried with mA, % and mbar but no luck). So far I have read all the manuals that I have found on Support Siemens and also many of the topics here on Forum. Has someone experienced the same problem perhaps ? Thank you in advance Kind regards Petar 
Last edited by: AutoGen_1049926 at: 10/01/2021 06:53:31 

10/1/2021 4:14 PM  
Joined: 3/28/2010 Last visit: 2/21/2024 Posts: 1005 Rating: (205)

I once ran into a situation with a DSIII where I could not change parameters with the pushbuttons because the DSIII had Yxx options that could only be overridden by using HART, ie a HART modem and PDM or Pactware. But I'm foggy on exactly which function it was. Whatever it was, it was not mentioned anywhere in the documentation. It took factory assistance to figure it out. If no one else pops up here (this is a user forum, not a factory help forum), you might have to submit service request to get it clarified. One note, I never used modes 2 and 3 because that's the wet calibration mode. In Modes 2/3, the transmitter matches the 4mA LRV or the 20mA URV to whatever the applied pressure at the moment the mode is actuated. Without having full blown calibration grade equipment to source a pressure, the results can be marginal, at best. The only application I know of where where Modes 2/3 were used was a level application where the plant had no idea what the dimensions of the vessel were and just want to make 20mA where 'the tank is full, where the level is at now', and then when the level dropped down to some low point, 'make 4mA where the level is now' (their words, not mine). For flow, in particular, where the primary flow element is sized for a given flow rate at a given DP, only Mode 6 should be used to enter the exact DP value for the 20mA URV that that is assumed to be the 100% value upon which the square root extraction is based (the max flow at 100% from the primary flow element sizing sheet). I'm not sure why Mode 5 (LRV) would be anything but 0.0. On the bench, with no applied pressure, any sensed pressure due to the diaphragm being of outofplumb will be reported as flow which could push the current output above 4.00mA if the square root function is SrLin or SrLi2 and not the SrOFF selection. 
10/2/2021 2:14 AM  
Joined: 4/28/2015 Last visit: 10/2/2021 Posts: 2 Rating: (0) 
Good morning, Thank you for answering. I have started "changing" parameters in MODE 2 and MODE 3 as I have seen that both of them are (for example) 4,02 mA , which was a total nonsense after I have switched back from SqLin to Lin in MODE 11. Also the MODE 5 and MODE 6 were messed up, also got some strange values. So far I have tried everything described in Manual(s) but the device seems not to be working like described in any of the manuals. I have readjusted the pressure in MODE 6 to 600mbar and like described, I am expecting to see the current max in MODE 3 to be 20mA, but this is not happening. In my believe this has to be a sequence of operation, or it has to do something to do with units (also, I made readjusting in %, mA and in my case mbar) but nothing helps. I need to operate only with magnetic buttons since I do not have HART programming device here on site nor Siemens PDM. In case You have an idea feel free to write. Thank You again for assistance Kind regards 
Last edited by: AutoGen_1049926 at: 10/02/2021 02:15:45Last edited by: AutoGen_1049926 at: 10/02/2021 02:16:35Last edited by: AutoGen_1049926 at: 10/02/2021 02:17:37 

10/2/2021 4:10 AM  
Joined: 3/28/2010 Last visit: 2/21/2024 Posts: 1005 Rating: (205)

Here's the rule, when you use mode 2 or 3 without a valid applied (calibration) pressure on the transmitter for the LRV (4.0mA zero) or URV (20.0mA span), you get garbage values for the LRV and URV. Those values will not make sense and there's no reason to try to make sense of what happened because you told the transmitter to scale itself to using invalid applied pressures. Skip and ignore modes 2 and 3. They are useless for a flow application. I assume 600mbar is the DP associated with the max flow rate for the primary flow element. Configure Mode 14 for mbar (engineering units) if it isn't already Mode 5 and 6 are used to manually enter values for LRV zero (4.0mA) and the URV span (20.0mA) values. No applied pressures are needed or used when Modes 5 and 6 are used, only values entered via the pushbuttons (or HART) are used. Mode 6 is the DP pressure value for 100% flow rate from the primary flow element sizing sheet. Enter 0.0 mbar for Mode 5 and enter 600mbar for Mode 6. Configure Mode 11 for SrLin instead of linear. The 420mA output will represent linear flow rate as the square root of the normalized value of DP as a percentage. 100% flow rate = 100% DP = 600mbar 90.0% flow rate = 81.0% DP = 486mBar 80.0% flow rate = 64% DP = 384mBar 70.0% flow rate = 49.0% DP = 294mBar 60.0% flow rate = 36.0% DP = 216mBar 50.0% flow rate = 25.0% DP = 150mBar 30.0% flow rate = 9.0% DP = 54mBar 20.0% flow rate = 4.0% DP = 24mBar 10.0% flow rate = 1.0% DP = 6mBar 
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