The scale range of positive pressure analog indicators shall have the normal reading fall within the ______ percentage of the gauge scale.

• A. 1/4
• B. 2/3
• C. 1/3
• D. 1/2

Answer: (B)

The idea is to place the normal operating pressure in the middle portion of the gauge so there’s room to swing up or down without hitting the ends. Analog gauges are most readable and accurate in the central part of their scale, and having the normal reading occupy about two-thirds of the scale gives ample headroom above and below for typical fluctuations. This helps prevent readings from drifting to the ends of the dial, which are harder to read and less reliable.

If the normal value sat only a smaller portion of the scale, there would be less room to accommodate changes, increasing the chance of the needle reaching the limit and making safe adjustments harder. A central two-thirds region balances readability, accuracy, and practical tolerance for variation, which is why the correct choice is two-thirds of the gauge scale.