Scientists design bomb-proof thermometer to measure the heat of explosions

Oct 08, 2008
The detonation of a small pyrotechnic charge in the NPL facility. A radiation pyrometer on the left side of the image observes the event. Image: NPL

Scientists at the UK's National Physical Laboratory (NPL) in Teddington have designed a high-speed thermometer that can measure the temperature inside explosions without being damaged in the impact.

The shockwave, heat, soot and debris from an explosion can damage thermometers. Conventional thermocouples do not react quickly enough to capture the information. This makes modeling the interaction of an explosion with its environment problematic – as temperature is essential in any calculations.

NPL scientists have now designed a reusable bomb-proof thermometer to understand the physical and chemical processes that occur during the detonation and expansion phases of an explosion. It is an optical fibre 400 microns (0.4 mm) across, protected from the blast by a sand-packed steel tube with one open end.

The thermometer detects thermal radiation at four different wavelengths, collecting more information about the thermal physics of the explosion than could be obtained from any one wavelength alone. The optical fibre probe collects thermal radiation, which is transmitted over a suitable safe distance to the main instrumentation.

To measure the temperature of the fireball, the thermometer was first calibrated up to 3000 K (2727 °C). This made it possible to convert the measured thermal radiation signals into temperatures. The thermometer can take 50,000 measurements per second, producing a detailed profile of temperature changes during a split-second detonation.


After a successful simple field trial NPL now hopes to examine much larger explosions. The findings will help to fine tune predictive models on many different explosion parameters.


NPL lead scientist, Gavin Sutton said:

"We produced a working prototype thermometer after some successful field trials and hope to measure the temperature of full-scale explosions in the near future. The lab tests involved temperatures of over 3000 kelvin and the only damage done was a small amount soot off the end of the optic fibre – which we easily removed with alcohol and a cotton bud."

Source: National Physical Laboratory

Explore further: The electric slide dance of DNA knots

add to favorites email to friend print save as pdf

Related Stories

Apple's fiscal 3Q earnings top analyst forecasts

6 hours ago

Apple's growth prospects are looking brighter as anticipation builds for the upcoming release of the next iPhone, a model that is expected to cater to consumers yearning for a bigger screen.

Recommended for you

IHEP in China has ambitions for Higgs factory

15 hours ago

Who will lay claim to having the world's largest particle smasher?. Could China become the collider capital of the world? Questions tease answers, following a news story in Nature on Tuesday. Proposals for ...

The physics of lead guitar playing

17 hours ago

String bends, tapping, vibrato and whammy bars are all techniques that add to the distinctiveness of a lead guitarist's sound, whether it's Clapton, Hendrix, or BB King.

The birth of topological spintronics

18 hours ago

The discovery of a new material combination that could lead to a more efficient approach to computer memory and logic will be described in the journal Nature on July 24, 2014. The research, led by Penn S ...

The electric slide dance of DNA knots

21 hours ago

DNA has the nasty habit of getting tangled and forming knots. Scientists study these knots to understand their function and learn how to disentangle them (e.g. useful for gene sequencing techniques). Cristian ...

User comments : 0