memory beta
 using a Geiger counter.

Spock using a Geiger counter.

A Geiger counter was a device used to measure radiation.

History and specifics

When he was transported from 2020 to 2270, Shaun Christopher saw Spock holding a tricorder and believed it looked like a Geiger counter. (TOS novel: The Rings of Time)

In 2266, Spock's Geiger counter detected radiation on the planet Numero Uno and learned that it was coming from nuclear weapon which Justin I and Justin II had stockpiled. (TOS comic: "The Ghost Planet")

In 2366, Geordi La Forge compared the merger of his VISOR and a tricorder to a Geiger counter. (TNG episode: "The Enemy")

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External links