PLC signal scaling
Convert between wire signal, raw ADC counts and engineering units — plus the slope and offset for your scaling block.
Result
4–20 mA carries a live zero: 4 mA means 'measuring zero', 0 mA means 'the loop is broken' — the reason current loops rule industrial floors.
How is this calculated?
Using the tool
The conversion every automation tech does daily: wire signal, ADC raw counts, and engineering units are one straight line. Set the three ranges, type a value in whichever domain you have — and read the other two, plus the slope and offset for your scaling block.
The math
Analog scaling is one straight line wearing three rulers. The transmitter maps your process range onto the signal range (4–20 mA carries 0–100% of the measurement), the input card maps the signal onto raw counts, and your scaling block maps counts onto engineering units: EU = m·raw + b, with m = span ratio and b pinning the zero. Every conversion here is the same fraction-of-span moved between rulers — which is why a mid-scale signal (12 mA on a 4–20 loop) is 50% of everything: counts, PSI, or degrees.
New to the math? Learn the concept: PLC basics, made visual