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SITRANS FCT030 CURRENT OUTPUT SCALING

Created by: azelcemp at: 3/21/2018 8:35 AM (4 Replies)

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3/21/2018 8:35 AM	Rate (0)
azelcemp Advanced Member Joined: 8/5/2017 Last visit: 9/12/2022 Posts: 38 Rating: (1)	Hello. I have SITRANS FCS400 sensor (DN25) linked to a remote SITRANS FCT030 transmitter. I want to use the 4-20mA output current and I need to configure the upper/lower scaling. Can anyone please help me find the range of the scaling values? tank you for your time.

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3/21/2018 4:46 PM	Rate (0)
azelcemp Advanced Member Joined: 8/5/2017 Last visit: 9/12/2022 Posts: 38 Rating: (1)	I found in the PRODUCT INFORMATION that Q_max = 17 700 kg/h for DN 25 size, wich is the same default value for the upper scaling mentioned in the Operating Instructions manual (4.9 kg/s) (see image in attachment) but what makes me confused is that the maximum range is 24.5 kg/s ( 88200 kg/H). Attachment output1_scaling.PNG (209 Downloads)

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3/22/2018 12:18 AM	Rate (0)
danw Gold Expert Joined: 3/28/2010 Last visit: 11/19/2024 Posts: 1081 Rating: (214)	Look carefully at Table C-54 (the table you posted) The default upper range value (as shipped from the factory) is 4.9 kg/s, which is a selected value within the minimum range value of -24.5 and the maximum range value of +24.5 kg/s. Pick a max flow value up to the +24.5kg/s maximum.

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3/22/2018 9:08 AM	Rate (0)
azelcemp Advanced Member Joined: 8/5/2017 Last visit: 9/12/2022 Posts: 38 Rating: (1)	So how can I pick the exact upper scaling, knowing that I don't have an idea about the range values of the flow going through the sensor ?!
	Last edited by: azelcemp at: 3/22/2018 9:47:52 AM
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3/22/2018 2:01 PM	Rate (2)
danw Gold Expert Joined: 3/28/2010 Last visit: 11/19/2024 Posts: 1081 Rating: (214)	If you don't know the flow, no one on the forum knows either. Ask whomever designed the system as to why they selected the size tube they did. What flow rate is anticipated. If you can't find that person or his notes, then it's empirical. Experimental. You need to run the system to see what kind of flow it has. The idea of picking a max value is to get the best resolution from the 4-20mA output. If your actual maximum never exceeds say, 12.3kg/s, then the system only uses about 25% (12.3 divided by 49) of the available resolution of the 4-20mA signal . Let's assume you only want forward flow, so the minimum is 0.0 flow; that ignores any back-flow, the negative range values. Initially set the upper range to 24.5k/s and do a couple runs and see what flow range is. If it's something like 12.3kg/s, then guess how much 'engineering growth' room is needed at the top end because your first trials might have been on the low side or some other product formulation requires 9% greater flow and reconfigure the 4-20mA output for 0-12kg/s or 0-14kg/s or whatever makes you feel good that day.

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