Which one of these statements is NOT a way to determine if an input is on or off?

The assertion made in the chosen answer reflects a misunderstanding of the question's intent. The focus is on identifying a statement that is NOT a method for determining if an input is on or off. Each of the other statements provides a clear method or context for determining the state of an input in a programmable controller system.

For instance, when considering the statement referring to a discrete input module using 12VDC, this voltage level establishes a clear threshold for distinguishing between the "on" and "off" states of the input. In practice, a technician would know that a certain voltage level indicates activation.

The mention of a normally open limit switch wired to a terminal outlines how physical switches can be utilized to interpret the on/off status. When the switch is closed, it alters the state of the circuit, providing definitive feedback on the input's status.

Lastly, discussing an Active High module gives specific expectations regarding the voltage readings at the terminal when the limit switch is in a closed position. This establishes a direct correlation between the state of the input and the expected electrical response.

Each of these statements essentially describes valid methods for determining the on/off status of inputs, which makes the option suggesting that all of these are ways to determine the input state a misinterpretation of