Which statement best describes zero and span adjustments in transmitter calibration?

Which statement best describes zero and span adjustments in transmitter calibration?

• A. They are global adjustments used for test mode.
• B. Zero and span determine the lower and upper ends of the output range and calibrate the range.
• C. They adjust only the digital display and have no effect on the actual signal.
• D. They are used to calibrate the power supply.

Answer: (B)

Zero and span calibrations define how the transmitter’s output maps to the measured variable. The zero setting anchors the lower end of the output when the input is at its minimum, while the span setting determines how much the output changes as the input moves from minimum to maximum. Together, they set the full-scale range and the slope of the response, so the transmitter can produce the correct output signal (for example, 4-20 mA) across the entire input span. This affects the actual signal in the loop, not just the display, and it’s distinct from any test-mode or power-supply adjustments.

Zero and span calibrations define how the transmitter’s output maps to the measured variable. The zero setting anchors the lower end of the output when the input is at its minimum, while the span setting determines how much the output changes as the input moves from minimum to maximum. Together, they set the full-scale range and the slope of the response, so the transmitter can produce the correct output signal (for example, 4-20 mA) across the entire input span. This affects the actual signal in the loop, not just the display, and it’s distinct from any test-mode or power-supply adjustments.