ANALOG INPUTS: HOW TO USE IT IN TIA PORTAL :

TIA PORTAL: ANALOG SIGNAL PROCESSING

An analog input is a continous signal coming from the field devices. Unlike the digital signals, analog input devices can give any values much greater than just 0 or 1.

 Temperature sensors, Level transmitters, Pressure transuducers, Flow meter etc. are common analog input devices. The signals comming from these devices usually measured as "0 - 10 volts", "1-5 volts", "0-20 ma", "4-20 ma".

 

PLC CPU:

To work with analog values, PLC devices must have analog IO channels. siemens PLC offers CPU which have analog IO channels.

You can add other Analog modules as per the process requirements.

To read values from an analog devices (not for the temperature sensor), use Conversion operations from the right corner in TIA Portal. 

1. NORM_X function:

You can use the instruction "Normalize" to normalize the value of the tag at the VALUE input by mapping it to a linear scale. You can use the MIN and MAX parameters to define the limits of a value range that is applied to the scale. The normal range for PLC is 0 to 27648. 

For normal range, the minimum value is 0 (zero), and maximum value is 27648.  Write these values in program. 

2. Scale_X function:

After normalizing the input value, we will scale it to show value in a range using Scale_X function. Scale_X functions scales the normalized value in the data type and value range specified by the minimum and maximum parameters.

Now start PLC SIM and change the input value to see change in the output value.

Temperature Measurement

For measurements of temperature, there are dedicated analog input modules for thermocouples and RTDs. 

The thermocouple (TC) modules (SB 1231 TC and SM 1231 TC) measure the value of voltage connected to the analog inputs. This value can be either temperature from a TC or volts. 

● If voltage, the nominal range full scale value will be decimal 27648. 

● If temperature, the value will be reported in degrees multiplied by ten (for example, 25.3 degrees will be reported as decimal 253). 

The RTD modules (SB 1231 RTD and SM 1231 RTD) measure the value of resistance connected to the analog inputs. This value can be either temperature or resistance.

● If resistance, the nominal range full scale value will be decimal 27648. 

● If temperature, the value will be reported in degrees multiplied by ten (for example, 25.3 degrees will be reported as decimal 253). The RTD modules support measurements with 2-wire, 3-wire and 4-wire connections to the sensor resistor

Therefore, we will use a division block in our project and divide the input value by 10. This input can be monitored in the PLC SIM.

Kindly Refer to our Youtube Video for better understanding :

TIA PORTAL: ANALOG SIGNAL PROCESSING