Abstract: A DC power supply comprising a pre-regulator having an input connected to a DC supply, a control terminal connected to a reference voltage and an output connected to an input of a three terminal integrated circuit (IC) voltage regulator. The IC regulator has an output terminal for connection to a load and an adjustment terminal connected to a bias voltage, a zener diode being connected between the control terminal and the output of the IC regulator and between the input and output of the IC regulator. The zener diode has a breakdown voltage less than a maximum permissible input-output voltage differential for the IC regulator whereby an excessive load demand tending to increase the input voltage to the IC regulator causes the zener diode to conduct and reduce the voltage on the control terminal of the pre-regulator which thereupon decreases the voltage to the input of the IC regulator.

Abstract: Sampling devices for detecting particulate contaminants, particularly radioactive particulate contaminants, in a gaseous medium, such as air. The devices use filters comprising a filter membrane sandwiched between two pieces of plastic material having holes exposing the filter membrane to the gaseous medium. Each filter is moved between a sampling position at which the filter is exposed to the gaseous medium and a measurement position at which the amount of particulate material collected by the filter can be measured. In the measurement position, a gas-tight seal may be formed with the plastic surrounding the filter medium so that the chamber holding the filter may be evacuated for measurement of radioactive particles. The filter may be moved linearly or rotationally. The detector may comprise a detector of radioactive particles.