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In programmable logic controller (PLC) programming, accurate data acquisition depends on proper scaling of input and output signals. Scaling factors convert raw sensor data into meaningful engineering units, ensuring precise control and monitoring.
Understanding Input Scaling
Input scaling involves converting the raw data received from sensors into a usable format. Raw signals often range from 0 to 1023 for 10-bit analog inputs or 0 to 65535 for 16-bit inputs. To interpret these signals correctly, scaling factors are applied.
The general formula for input scaling is:
Scaled Value = (Raw Input / Max Raw Value) × Engineering Range + Offset
Calculating Output Scaling
Output scaling converts control signals from engineering units back into raw values suitable for actuators or other devices. This process ensures that the output signals accurately represent the desired physical quantities.
The formula for output scaling is similar to input scaling:
Raw Output = ((Desired Engineering Value – Offset) / Engineering Range) × Max Raw Value
Determining Scaling Factors
To calculate the scaling factors, identify the sensor’s raw data range and the corresponding physical measurement range. For example, if a temperature sensor outputs 0–1023 corresponding to 0–100°C, the scaling factor is:
- Scaling factor = 100°C / 1023
- Offset = 0°C (if zero-based)
Applying these calculations ensures that raw data is accurately translated into meaningful units, facilitating precise control in automation systems.