How do you perform zero and span calibration on a pressure transmitter using a deadweight tester?

• A. Use electrical zero; adjust sensor.
• B. Apply known pressures at zero and full scale using the deadweight tester; adjust zero to match zero input and span to match full-scale input, verify across range.
• C. Replace transmitter.
• D. Not calibrate.

Answer: (B)

Zero and span calibration for a pressure transmitter is about setting the instrument so its output matches actual pressures across its range. The key is using a precise, known pressure source, like a deadweight tester, to define both ends of the scale.

First, generate zero pressure (no applied load) with the deadweight tester and observe the transmitter’s output. Adjust the zero control so that the output corresponds to zero input pressure. Next, apply full-scale pressure with the tester and adjust the span (gain) so the output matches the full-scale input. After both adjustments, verify the span by checking mid-range and other points in between to ensure the output is linear and accurate across the range.

Using the deadweight tester matters because it provides traceable, repeatable pressure values, ensuring the zero and span adjustments align the transmitter’s electrical signal with actual pressures. Relying on electrical zero alone or skipping calibration would not correct the sensor’s offset and slope, and replacing the transmitter or not calibrating would leave the instrument unverified and inaccurate.