Abstract: A radiation detector can perform both rate and dose measurements for personal safety and also to provide measurements that are sufficiently sensitive for security applications. In one embodiment, a radiation detector has a first measurement channel and a second measurement channel, where the second measurement channel can measure radiation at levels that would saturate the first measurement channel. The detector can automatically switch between the high and low sensitivity channels while continuously integrating the measured rates to determine a radiation dose. The detector can also conserve power by automatically shutting off the unused measurement channel and still give a personal safety warning when the radiation rate or the dose reaches respective alarm thresholds.

Abstract: An oxygen sensor includes a solid polymer electrolyte, e.g., on an acid treated Nafion membrane and uses a diffusion-limited fuel cell type reactions. The sensor avoids electrolyte leakage and avoids consumption of electrodes. In different configurations, a counter or reference electrode can be on the same or the opposite side of the electrolyte as a sensing electrode. An insert limits and controls oxygen diffusion into a sensing chamber containing the sensing electrode that catalyzes reduction of oxygen. Applying appropriate bias voltages to the reference and sensing electrodes causes an output current of the sensing electrode to be proportional to the rate of oxygen consumption based on Frick's law under a diffusion-limited mode. The output current can be measured, e.g., using a resistor to convert the current to a voltage signal.