Attention members: billing update happening now. Learn more.

  • CCST
ISA Certified Control Systems Technician (CCST) program

Certified Control System Technicians (CCSTs) calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables.

CCST question

As outlined in ANSI/ISA 5.1-2009, Instrumentation Symbols and Identification, an instrument that is monitored on the control system HMI and is part of a safety instrumented system (SIS) loop would be represented by which type of symbol on a process and instrumentation diagram?

A. A circle contained in a box with a horizontal dashed line through the circle.
B. A hexagon with a double-dashed line through it, not contained in a box.
C. A diamond contained in a box with a horizontal solid line through the diamond.
D. There is no representation for a SIS instrument given in ANSI/ISA 5.1-2009.

CCST Answer

The correct answer is C,“A diamond contained in a box with a horizontal solid line through the diamond.”

CCST May/Jun fig 1

The diamond symbol was first defined for safety instrumented systems with the release of ANSI/ISA 5.1-2009. Per previous releases, a box around the instrument “bubble” with a solid horizontal line through it indicates that the measurement or control element is normally accessible to the operator from the main operator console, typically a human-machine interface (HMI) screen in modern control systems.

Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, Second Edition, ISA, 2005.

Reader Feedback

We want to hear from you! Please send us your comments and questions about this topic to

Like This Article?

Subscribe Now!

About The Author