The accuracy of digital indicators shall be +/- ____ % of the operating pressure at which they are used.

• A. 4
• B. 2
• C. 5
• D. 1

Answer: (C)

Digital indicators in medical gas systems are designed to show pressure with a tolerance that scales with the pressure itself. The intent is to keep readings reliable across the entire operating range, so the specified accuracy is a percentage of whatever pressure the system is currently at.

The best choice sets that tolerance at plus/minus five percent of the operating pressure. This means at 100 psi the reading could be off by up to 5 psi, and at 400 psi up to 20 psi. This level of accuracy is a practical balance between safety and cost, providing consistent reliability across low and high pressures without requiring ultra-tight tolerances.

Tighter tolerances like 4%, 2%, or 1% would demand more precise calibration and higher costs, and are not typically required for this purpose in standard practice.