diameter of a circle with area equal to the device projected capture area Note 1 to entry: The equivalent diameter is generally calculated as: $D}_{e}=\sqrt{\frac{4A}{\pi}}{D}_{\text{E}}=\sqrt{\frac{4A}{\pi}$, where A is the projected capture area as illustrated in Figure 3. Key A  projected capture area  h  height  w  width  D_{E}  equivalent diameter  R  radius    Figure 3 – Equivalent diameter calculations for various projected capture areas
