Question

The most common pneumatic signal standard for industrial process instruments is:

• A. (0-20) psi
• B. (3-15) psi
• C. (4-20) psi
• D. (0-10) psi

Hint:

For pneumatic instruments, remember: \textbf{4-20 psi} is the standard for most industrial processes, providing a reliable and fault-free signal range.

Answer 1

The Correct Option is C

In industrial process control systems, pneumatic instrumentation typically uses a standardized pressure signal range to communicate information between devices like transmitters, controllers, and actuators.
The most common pneumatic signal standard is the 4-20 psi range. Here's why:
- The range of 4 psi to 20 psi is used because it allows for live zero functionality. This means that a pressure of 4 psi indicates the minimum value of the measurement (e.g., 0% of the range), while 20 psi indicates the maximum value (e.g., 100% of the range).
- This ensures that the instrument is always reading above zero pressure, eliminating the possibility of a zero-pressure signal being mistaken for a system fault.
- The 0-20 psi range is not commonly used, as it lacks the benefit of live zero. The 3-15 psi range is sometimes used in specialized applications but is less common.
Thus, the correct pneumatic signal standard for industrial instruments is 4-20 psi.