Martins_Eng

I have a doubt, I will control the flow of a given liquid, I use the analog input of the PLC in 4-20mA, using a FC105 to scale the problem and the ceiling is to put the maximum possible flow in the system, and to have a ratio of 4 mA = 0 m³ / min and 20 mA = 15m ³ / min.
And I'm using to control the pid of FB41 S7-300, just do this to commission the flow?

I have porceder this way.

To do the control task completely, you need an analog output
channel.Samples on configuration of FB41 is available here.
Standard PID Package - FB41 Samples

Of course you need to tune the loop,You can set initial value selected
for Ti and Td(and Tm_lag) or use tables for tuning provided in this book.
Also you have option of using valuable information shared by Forum's
members here(PID tunning.zip ).

Best regards,
hdhosseini

Martins_Eng

Okay, I'm using FB41, but the content you sent me and a great, very useful, and in relation to the HI_lim FC105 and only use the maximum flow that I have to be converting 4-20mA for 0 to 15 m³ / min.

For one to use to use an RTD entenho HI_lim of 27,648 for the scale

Description:
You can use the FC 105 "SCALE" function for measuring voltage, current, temperature and resistance.

The following holds for temperature measurements:

• With resistance thermometers configured in the standard range and with thermoelements, the analog input gives the 10-fold temperature value as integer.
  Example:
  The integer value 600 corresponds to a temperature of 60.0°C. Set a high limit HI_LIM and low limit LO_LIM of +2764.8 and -2764.8 respectively to avoid a division by 10.
  
• With resistance thermometers configured in the climate range, you get the 100-fold temperature value as integer.
  Example:
  The integer value 2500 corresponds to a temperature of 25.0°C. Set a high limit HI_LIM and low limit LO_LIM of +276.48 and -276.48 respectively to avoid a division by 100.