ASNT Industrial Radiography Radiation Safety Practice Test

How must a survey meter be calibrated for accuracy?

1. At the zero mark only

2. On each scale at one-half scale only

3. At two points: one-third and two-thirds of each scale

4. At the highest range only

The correct answer is: At two points: one-third and two-thirds of each scale

Calibration of a survey meter for accuracy is essential to ensure reliable radiation measurements. The correct approach involves calibrating the meter at two specific points: one-third and two-thirds of each scale. This method provides a comprehensive understanding of the instrument's performance across its entire range, not just at the extremes or the midpoint. Calibrating at one-third and two-thirds ensures that the measurements taken at various levels reflect the true radiation levels accurately. It accounts for any non-linearity that may exist in the meter’s response across its range, which helps in verifying that the readout remains consistent and accurate under different operating conditions. In contrast, calibrating only at the zero mark, at one-half scale, or at the highest range alone would not adequately assure the accuracy of the instrument throughout its entire operational range. Each of these approaches could miss potential errors in reading or response at other significant points on the scale, leading to discrepancies during actual measurements in industrial radiography settings.