Why Scaling is Done in PLC

Programmable Logic Controllers (PLCs) are widely used in industrial automation to monitor, control and manage machinery and other equipment. One of the essential functions of PLCs is signal processing. The incoming signals are measured and scaled to control the output devices. This article will explore why scaling is done in PLC programming, its importance, and how it works.

 

1. Importance of Scaling

 

Scaling is an essential function in PLC programming because it ensures that the data being measured and processed is within a predefined range. Scaling allows PLCs to interpret raw sensor data into usable values that can be processed to execute the required functional output. Scaling ensures that the data outputted by the sensors are accurate in value range, enabling the system to produce reliable and consistent results.

 

 

2. How Scaling Works

 

To understand how Scaling works, consider a temperature measurement system, where the temperature reading of a thermocouple is to be sent to the PLC. The voltage generated by the thermocouple is converted to a temperature value by an Analog-to-Digital Converter (ADC) before the PLC processes it. The data received by the ADC is given in raw unit values, rather than a temperature value.

 

The raw value must be converted to the correct temperature value range for proper processing by the PLC device. Scaling factors are used to transform the raw signal into its correct temperature. The scaling factor is derived by using a linear or non-linear equation that maps the input signals in volts or milliamperes to a range of scales.

 

 

3. Typical Scaling Parameters

 

PLC scaling relies on a linear scaling function that uses slope and intercept to convert raw sensor values into industrial parameters within a defined range. The slope is the rate of change estimate, while the intercept is the value of the offset. The formula used to determine the scaled value of a signal in a PLC is:

Scaled value = Raw signal x (Maximum scale value - Minimum scale value) /
               (Maximum raw value - Minimum raw value)

Where:
- Scaled value is the value of output after scaling
- Raw signal is the unscaled value received from the sensor
- Maximum scale value and Minimum scale value are the minimum allowed values of the signal range.
- Maximum raw value and Minimum raw value are the raw signal values corresponding to the maximum and minimum allowed values of the scale.

 

 

4. Benefits of Scaling

 

Scaling offers several benefits in the world of PLC programming:

- Data accuracy: scaling ensures that the data being processed has accurate information and data to produce reliable results.
- Reduction of Data Overload: Scaling of signals reduces the amount of data required for processing by taking out irrelevant data.
- Ease of interpretation: Scaled parameters reduce the complexity of signal interpretation while simultaneously providing accuracy, and efficient processing.

 

Conclusion

 

In summary, scaling is an essential programming function in PLCs. It ensures the accuracy of raw sensor measurements by processing and interpreting data received from the sensors within a defined range. The key advantages of scaling include improved reliability, data accuracy, and reducing the amount of data processed by the PLC device. Scaling ensures reliable and accurate results, provided the correct range of scaling parameters is used. Therefore, Scaling is critical to the proper functioning of industrial control systems.