Explain the difference between two-point and multi-point calibration and when to use each.

• A. Two-point uses two reference points to define linear response; multi-point uses several points to correct nonlinearities; use two-point for linear sensors with limited range; multi-point for wide range or nonlinear response.
• B. Two-point uses two temperatures; multi-point uses two voltages.
• C. Two-point calibrates humidity; multi-point calibrates pressure.
• D. Two-point calibrates with zero and full-scale automatically; multi-point requires environmental enrichment.

Answer: (A)

Two-point calibration relies on a straight-line relationship between input and output, determined by two known reference points. It’s fast and simple, and it works well when the sensor behaves linearly over the range you care about or you only need accuracy at a limited span (often at zero and full-scale). By using those two points, you define the slope and offset that map measurements to true values.

Multi-point calibration adds more reference points and lets you map a curved, nonlinear response. By fitting a curve through several known input-output pairs, you can correct for nonlinearities and maintain accuracy across a wider range. This approach is essential when the sensor’s response isn’t linear throughout its operating span or when high accuracy is required across many points.

In short, use two-point when the sensor is effectively linear in the needed range and you want a quick, simple setup. Use multi-point when you need good accuracy over a wide range or when the sensor shows nonlinear behavior that a straight line can’t capture.