For a phototimer to function properly, which actions must the technologist perform?

• A. Calibrate the X-ray generator and photo-timer circuits per intensifying screens.
• B. Position the patient over the correct photo-timer sensor panel.
• C. Ensure that the part being examined covers the entire chamber.
• D. All of the above.

Answer: (D)

A phototimer (AEC) works reliably only when the system is properly set up and the exposure field is aligned with the sensor. Calibrating the X‑ray generator and photo-timer circuits to the specific intensifying screens ensures the sensor’s response matches the expected exposure for that screen speed. If this calibration isn’t correct, the timer won’t terminate at the right moment for the chosen screen, leading to inconsistent densities or repeats.

Placing the patient over the correct photo-timer sensor panel is essential because the sensor must be irradiated by the patient’s anatomy in the field of interest. If the sensor isn’t under the area being imaged, the exposed signal will misrepresent the actual anatomy, causing under- or overexposure.

Making sure the part being examined covers the entire chamber guarantees the sensor receives information from the intended area and that the exposure is terminated based on the correct region. If any part of the chamber is outside the field, the timer might respond to signals from unintended areas, again compromising image quality.

All of these actions together ensure the phototimer functions as intended, producing consistent, diagnostic images with the correct exposure.