Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

PRESSURE TRANSMITTER SCALING???

Created by: sundar at: 11/15/2008 11:52 AM (8 Replies)

Rating (0)

Thanks 1

9 Entries

11/15/2008 11:52 AM	Rate (0)
sundar Posts: 100 Rating: (2)	I am new one in analog. i should make show the pressure transmitter value in mmi screen. i am using 0 - 70 bar PT. how can i display the pressure using current input(4-20ma)
sundar Posts: 100 Rating: (2)
Suggestion To thank Quote Answer

11/15/2008 1:55 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 11/18/2024 Posts: 12296 Rating: (2691)	Hello sundar; There is a scaling function available in Step 7, in the LAD/STL/FBD editor, TI-S7 converting blocks, FC 105 "SCALE". FC 105will take an analog value as an input (PIWxxx address, your pressure transmitter input), allow you to setup the engineering value limits (your pressure limits: 0-70 bar) and will return a REAL value as a result. This will be a floating-point value (ex. 32.5) representing your analog signal in bars. Try a Search on the forum, on SCALE or on FC 105; the subject has been discussed a few times. Hope this helps, Daniel chartier
	Last edited by: dchartier at: 11/15/2008 2:00 PM
Suggestion To thank Quote Answer

11/25/2008 7:10 AM	Rate (0)
sundar Posts: 100 Rating: (2)	Hi to all i have a doubt about scaling. i use also flow meter . the range (0 to 9 m3/hr). i am using unipolar (bipolar input is off)so the input integer value is assumed to be between 0 and 27648, i attached the program shapshot below. my question is 1) If the flow value 0m3/hr the input integer value is also should be minimum value(0) 2) If the flow value 9m3/hr the input integer value is also should be maximum value(27648) is it correct or not. The flow meter showing value comes in out as real. Attachment flow scale.JPG (631 Downloads)
sundar Posts: 100 Rating: (2)
Suggestion To thank Quote Answer

12/10/2008 4:47 AM	Rate (0)
Damha Posts: 6 Rating: (0)	Hallo Sundar, For your question, in function SCALE maybe in the easy word i can explain like this : 4 mA is equal than 0 decimal 20 mA is equal than 27648 decimal and if you put range value output, for example, 0.0 - 100.0 so: 4 mA --> 0.0 20 mA --> 100.0 and if setting of your sensor 0 m3/h = 4 mA and 9 m3/h = 20 mA so 0 m3/h = 0.0 9 m3/h = 100.0 and yes, value output is real. I hope its help. Regard, Damha
Damha Posts: 6 Rating: (0)
Suggestion To thank Quote Answer

1/16/2009 9:06 PM	Rate (0)
gerryh Posts: 1 Rating: (0)	How do I compensate if the analog card is 8 bit? Does FC105 care what resolution the input signal is?
gerryh Posts: 1 Rating: (0)
Suggestion To thank Quote Answer

1/17/2009 10:05 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 11/18/2024 Posts: 12296 Rating: (2691)	Hello gerryh; The binary representation of an analog value from the periphery in Siemens PLCs is independant of the resolution of the analog module used. Whether your module is 8-bit or 16-bit, the numerical value of an analog input or outputwill always be represented from 0 to 27648 (unipolar value) or -27648 to +27648 (bipolar value). What will change is the internal resolution of the analog value, that is the steps that the value will take for an 8-bit module wioll be larger, while for a higher-resolution module the steps will be finer. If you need to convince yourself of this, please study the chapter on Analog Value Representation in the manual S7-300 Module Data: S7-300 Automation System Module data So, to answer your exact question, FC105 will scale the numerical value of the analog input to the engineering values you set, whether the module has an 8-bit resolution or 16-bit resolution. Hope this helps, Daniel Chartier

Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Pioneer

12/19/2009 9:13 AM	Rate (0)
ab1234 Posts: 9 Rating: (0)	Dear dchartier You are right for analog signals for current and voltage measurement. But not true for all tyoes of signals, for example Pt100. In case of Pt100, the values range from -2000 to 8500. Though for Scaling purpose, the result will not be affected if properly parameterized. Thanks
ab1234 Posts: 9 Rating: (0)
Suggestion To thank Quote Answer

12/19/2009 1:58 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 11/18/2024 Posts: 12296 Rating: (2691)	Hello ab1234; You are right, of course, about the PT100/1000 ranges. Notice in this case that the numerical value read in from the analog module only requires a division by 10 (best results are obtained if you convert the peripherical value to a REAL, and then divide by 10.0) in order to read the temperature. Refer to the manual proposed earlier for more details. Glad you pointed this out, Regards, Daniel Chartier
	Last edited by: dchartier at: 12/21/2009 9:11 PM
Suggestion To thank Quote Answer

2/3/2010 12:50 AM	Rate (0)
ivan_euler Posts: 54 Rating: (0)	in scaling checked first whether your using it as 2 wire system or a four wire system...... It should match the configuration at the back of the analog input and also set it right at the hardware configuration at the simatic manager then used the scaling blocks or you could write your own code for better understanding the scaling function
ivan_euler Posts: 54 Rating: (0)
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on