8/16/2019 7:38 PM | |
Joined: 1/3/2019 Last visit: 12/16/2022 Posts: 64 Rating: (0) |
Hi dear experts.. I test that link and every thing work ok.. I'm new on flow totalizers.. I set input value as REAL and flow totalizer start counting and add numbers.. how can i understand relation between 4-20ma output from flowmeter and this value as output in that block?? Mr. Hosseini can you describe it for me? Thans ------------------------------------------------------------------------------------------ |
Last edited by: M.Abzadeh at: 08/16/2019 19:41:42Last edited by: Jen_Moderator at: 08/19/2019 07:25:39New subject after splitting En. M.ABZADEH |
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8/16/2019 11:24 PM | |
Joined: 9/27/2006 Last visit: 9/25/2024 Posts: 12283 Rating: (2685)
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Hello M.Abzadeh; If you study the introductory text of the original link provided, you will see that one of the inputs to the totalizer FB is "Value", a measurement (in REAL format) that you want to totalize. So, if you want to obtain a totalized value in gallons per minute coming from your flowmeter, your input Value would represent gallons, and the input Interval would be 1 min in the FB. But the reading you get from your flowmeter is a 4 to 20 mA instantaneous reading; you need a instantaneous value in gallons as an input to the totalizer functrion. To go from the current measurement to an engineering value (gallons) you must scale the flowmeter output. So use the scaling functions below to transform a 4-20 mA measurement to a gallons (for example) value (REAL), then use the output of the scaling function as an input to the totalizer function. To scale an analog value in a S7-300 or S7-400 PLC you should use the FC 105 ("SCALE") from the TI/S7 converting library to accomplish this: How and for which analog measurements can you use the function FC105 "SCALE" to convert the integer values (INT) into real number values? https://support.industry.siemens.com/cs/ww/en/view/1765297 For a S7-1200 or S7-1500 PLC teh equivalent functions would be Norm_X and Scale_X: For an S7-1200/S7-1500 controller in STEP 7 (TIA Portal), how do you scale integer values in real numbers and vice versa for analog inputs and outputs? https://support.industry.siemens.com/cs/ww/en/view/39334504 Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 08/16/2019 23:45:22 |
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8/17/2019 10:02 AM | |
Joined: 1/3/2019 Last visit: 12/16/2022 Posts: 64 Rating: (0) |
Dear Mr.dchartier... Thank you very much for your detailed explanation... |
En. M.ABZADEH |
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8/19/2019 3:30 PM | |
Joined: 9/27/2006 Last visit: 9/25/2024 Posts: 12283 Rating: (2685)
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Hello M. Abzadeh; I do not remember ever saying that : "pulse value can be used as input to the totalizer block". The Value input to the totalizer block always must be an engineering value (in REAL format), not a number of pulses.So you must count the number of pulses and mutiply them by the factor (sometimes known as the K-factor) you have set on your flowmeter (liters/per pulse, gallons per pulse, m3 per pulse...); this will give you an engineering value in liters, gallons, m3 ,,, This engineering value (converted to REAL) can be totalized fy the totalizer FB. Look at any manual for a flowmeter with pulse output, for example this one: https://www.coulton.com/res/transit_time_flowmeter_fusion_manual_01_11.pdf Note that this particular unit also provides for a 4-20 mA output, and a built-in totalizer. this is ofyten the case with such flowmeters. In that case you might decide to sue the integrated totalizer and use the 4-20 mA signal to send the totalized value to your PLC at regular intervals. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 08/19/2019 15:34:02 |
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This contribution was helpful to1 thankful Users |
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