Geiger counter

A Geiger counter was a piece of technology involving radiation that made a ticking noise. The First Doctor considered it to be advanced technology. It included a needle on a scale that could reach a "danger point". (TV: "The Survivors")

Humans used the technology. In 2013, Kate Sherrin monitored the changes in radiation on the shoreline of Ambermouth using a Geiger counter. (AUDIO: Eldrad Must Die!)

A Geiger counter was used on Recovery 7 when it was brought back to Space Control. It detected levels of radiation in the ship's interior which were so high that its setting was on maximum. (TV: The Ambassadors of Death)

The First Doctor had such a device, but it broke during his first travel with Ian and Barbara. The TARDIS control console was capable of measuring radiation, though the one in the Doctor's TARDIS experienced a delay in activation when it first arrived on Skaro. (TV: An Unearthly Child)

The Daleks made use of one, and the Doctor, Susan Foreman and Ian once encountered it while searching for mercury in the Dalek City. It revealed to them the high level of radioactive fallout in the atmosphere, which resulted in a jungle being turned to stone, the soil becoming barren, and radiation poisoning among the three. (TV: "The Survivors") When the group later returned to Skaro, the Doctor consulted his TARDIS' geiger counter to confirm that radiation levels were now within acceptable tolerance. (AUDIO: Return to Skaro)

When the TARDIS crew found themselves on the Tick-Tock World, Ian, Barbara and Susan initially mistook the growls of the Xesto for a geiger counter, briefly wondering if the planet might be radioactive. (AUDIO: Tick-Tock World)

The equipment of the soldiers of the Combined Galactic Resistance was provided with such technology. It helped to diagnose a radiation leak as the cause of malfunctions within a Dalek. (TV: Into the Dalek)