PLC Analog Scaling Calculator

Understanding PLC Analog Scaling

In industrial automation, analog signals (like 4-20mA current loops or 0-10V voltage) represent physical quantities such as temperature, pressure, or flow. To use these signals in a PLC program (like Siemens TIA Portal or Mitsubishi GX Works), you must scale the raw integer value into a meaningful engineering unit.

The Linear Interpolation Formula

This calculator uses the standard linear equation y = mx + b to perform the conversion. The formula used is:

This is identical to the logic used in the NORM_X and SCALE_X instructions in Siemens S7-1200/1500, or the SCL instruction in Mitsubishi FX series.

Common PLC Raw Data Ranges

Different PLC manufacturers use different integer ranges to represent analog signals. Here is a quick reference table:

PLC Brand / Series	Analog Resolution	Raw Integer Range (Int)
Siemens S7-1200 / S7-1500	12-bit / 13-bit	0 to 27648
Siemens S7-300 / 400	Various	0 to 27648
Mitsubishi FX3U / FX3G	10-bit / 12-bit	0 to 4000 (or 0-16000)
Allen-Bradley (Rockwell)	CompactLogix	0 to 32767 (Typical)
Omron CP1H / CP1L	High Resolution	0 to 6000 or 0 to 12000

Frequently Asked Questions