Bombproof thermometer

A high-speed thermometer that can withstand the impact of bomb explosions has been designed by scientists at the National Physical Laboratory (NPL).

Up until now, the analysis of an explosion's interaction with its environment has been problematic. Thermocouples are too slow to capture accurate data and the resulting shockwave, heat, soot and debris of an explosion can damage traditional thermometers.

NPL scientists have completed the design of a reusable, bombproof thermometer, which consists of a 400 microns optical fibre protected by a sand-packed steel tube that is open at one end.

The thermometer is reportedly able to measure thermal radiation at four different wavelengths, enabling the collection of more detailed data than would normally be possible. The information is then transmitted over a safe distance to the central instrumentation via the optical fibre probe.

The new design is capable of producing 50,000 measurements per second, providing a detailed account of temperature changes during split-second detonation.

The thermometer was initially calibrated up to 3,000K (2727 °C) to measure the temperature of the fire ball. This allowed scientists to calculate the temperature with the data produced from thermal radiation signals.

Following a successful field trial, NPL hopes to measure the temperature of full-scale explosions in the near future. The results will allow for a better accuracy rate of predictive models in various explosion parameters.