CAS Study Guide 2026
Everything you need to pass the CAS exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 CAS Exam Format at a Glance
📚 CAS Topics to Study (17)
✍️ Sample CAS Questions & Answers
1. What is the primary limitation of a thermocouple compared to an RTD for temperature measurement?
Thermocouples require cold junction (reference) compensation and typically have lower accuracy and repeatability than RTDs.
2. What does the term 'proof test interval' mean in the context of safety instrumented systems?
The proof test interval is the time period between full functional tests of a SIS to reveal and correct hidden dangerous failures.
3. Which pressure measurement term describes pressure referenced to absolute zero (perfect vacuum)?
Absolute pressure is measured relative to absolute zero pressure (perfect vacuum) and equals gauge pressure plus atmospheric pressure.
4. What is the purpose of a 'terminating resistor' at each end of a PROFIBUS or RS-485 network?
Terminating resistors match the cable's characteristic impedance, absorbing signal energy at the cable ends to prevent reflections that would corrupt data.
5. Which communication protocol is commonly used for industrial automation?
Modbus is a widely used protocol that allows communication between automation devices and control systems.
6. According to ISA-18.2, what is the correct term for an alarm that is continuously in the alarm state for more than a defined period?
ISA-18.2 defines a 'standing alarm' as one that remains active (unacknowledged or acknowledged but not resolved) for an extended period.