# AutoQuiz: How Do You Calculate Highest Pressure Differences?

AutoQuiz is edited by Joel Don, ISA’s social media community manager.

Today’s automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for information about the CCST program. This question is from the Level I study guide, Domain 1, Calibration. Level I represents a professional who has a five-year total of education, training, and/or experience.

Which of the following will have the highest pressure difference between the surface and 6 inches below the surface?

a) a 12-in-vertical straw filled with water
b) a 10-ft-diameter open tank filled with water
c) a 5-ft-diameter vertical pipe filled with water
d) a 7-ft-diameter vertical pipe filled with water
e) none of the above, because the pressure difference in each is the same