Analog signals

Analog signals are 0–10 V. Analog wires are drawn in orange. The value of a potentiometer or transmitter is set in simulation with a large slider (click the symbol).

Sources

• Potentiometer: connected between two potentials; the wiper gives a fraction of the end voltage (for example 0–10 V between L+ and M of a 10 V supply, or 0–24 V on a 24 V supply).
• Transmitter 0–10 V, 3-wire (L+, U, M): measures temperature, pressure, level, flow or distance with a configurable range and unit; needs 15–30 V DC and outputs 0–10 V proportional to the value.

PLC analog inputs

Each model converts 0–10 V to its own raw value, shown live next to the input in simulation:

SCALE and UNSCALE

In Ladder, SCALE converts a raw analog input into an engineering value with a name (for example TEMP, 0…100 °C) that comparisons can use: OUT = MIN + IN / RAW_MAX · (MAX − MIN). UNSCALE does the opposite: it takes a value or a name (for example a set-point 0…100 %) and writes the raw value to an analog output. Together they let a potentiometer set the speed of a motor through the PLC.

Analog outputs and inverters

The generic PLC can have 0–10 V analog outputs (AQ). A frequency inverter takes 1~ 230 V in, gives 3~ out, and is controlled by DI1 (forward), DI2 (reverse — both = stop) and AI (0–10 V = 0…f_max). The three-phase motor shows the resulting frequency, direction and speed.