The actual exposure time must be accurate within what range when the assigned exposure time is 100 milliseconds (ms)?

The actual exposure time must be accurate within what range when the assigned exposure time is 100 milliseconds (ms)?

• A. +/- 2.0 ms
• B. +/- 10.0 ms
• C. +/- 1.0 ms
• D. +/- 5 ms

Answer: (D)

The timer’s accuracy is assessed as a percentage of the indicated exposure time. For a 100 ms exposure, a tolerance of ±5 ms means the actual exposure must fall between 95 ms and 105 ms. This 5% window provides a practical balance, allowing minor electronic or mechanical variations while keeping image receptor exposure and patient dose consistent. A tighter tolerance (±1–±2 ms) is too strict for typical equipment, and a looser one (±10 ms) would introduce too much variation in exposure. Hence, the acceptable range is ±5 ms.

The timer’s accuracy is assessed as a percentage of the indicated exposure time. For a 100 ms exposure, a tolerance of ±5 ms means the actual exposure must fall between 95 ms and 105 ms. This 5% window provides a practical balance, allowing minor electronic or mechanical variations while keeping image receptor exposure and patient dose consistent. A tighter tolerance (±1–±2 ms) is too strict for typical equipment, and a looser one (±10 ms) would introduce too much variation in exposure. Hence, the acceptable range is ±5 ms.