What is essential for the operation of a radiation survey instrument?

The operation of a radiation survey instrument relies heavily on its accuracy, which is why calibration is essential. Calibrating the instrument periodically ensures that it provides reliable and precise measurements of radiation levels. This process adjusts the instrument's readings to align with known standards, which may change over time due to sensor drift or environmental factors. A properly calibrated instrument helps operators to accurately assess radiation exposure, ensure safety, and comply with regulatory requirements.

The other options, while they may seem beneficial in certain contexts, do not universally apply as essential functions for all radiation survey instruments. For instance, measuring only beta radiation restricts the instrument's utility, while being waterproof may be necessary for specific environments but is not a fundamental requirement for all applications. Digital models can offer advantages such as easy data logging or enhanced display features, but the accuracy of measurements is the paramount concern for effective radiation monitoring. Therefore, the key factor for the successful operation and reliability of a radiation survey instrument resides in its periodic calibration for accuracy.