A unipolar module can accept an input signal that varies in the positive direction only.

• A. True
• B. False
• C. It can vary in both directions
• D. It varies randomly

Answer: (A)

Unipolar inputs are read with respect to a single polarity, typically ground, so the allowable range is from zero up to a positive maximum. A unipolar module therefore accepts signals that vary in the positive direction only. Negative values are outside its design range and wouldn’t be read correctly (or could cause damage), which is why this statement is true. If a system needed to measure both positive and negative voltages, a bipolar module would be used. The other options describe negative variation, both-direction variation, or randomness, none of which apply to a unipolar input.