How do you scale analog inputs and outputs in PLC programs?

Analog scaling converts raw A/D counts or standard signals to engineering units. Formula: EU = (Raw - Raw_Low) * (EU_High - EU_Low) / (Raw_High - Raw_Low) + EU_Low. For 4-20 mA with 0-100 psi: Raw range 4-20 maps to 0-100 psi. Most PLCs have built-in scaling instructions (SCL, linear interpolation). Handle out-of-range conditions (signal failure <4 mA). For outputs, reverse calculation. Consider resolution (12-bit = 4096 counts, 16-bit = 65536 counts) affecting precision. Test scaling with known inputs during commissioning. Square root scaling needed for differential pressure flow.