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: Thermoelectric power plants could offer economically competitive renewable energy

add to favorites email to friend print save as pdf

Related Stories

2012 movie massacre hung over 'Interview' decision

6 minutes ago

When a group claiming credit for the hacking of Sony Pictures Entertainment threated violence against theaters showing "The Interview" earlier this week, the fate of the movie's big-screen life was all but ...

SDO captures images of two mid-level flares

31 minutes ago

The sun emitted a mid-level flare on Dec. 18, 2014, at 4:58 p.m. EST. NASA's Solar Dynamics Observatory, which watches the sun constantly, captured an image of the event. Solar flares are powerful bursts ...

Report: FBI's anthrax investigation was flawed

46 minutes ago

The FBI used flawed scientific methods to investigate the 2001 anthrax attacks that killed five people and sickened 17 others, federal auditors said Friday in a report sure to fuel skepticism over the FBI's ...

Recommended for you

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.