Sense globe

According to the pamphlet, "Anatomy of the Dalek", sense globes dotted the base unit of the Dalek casing, (COMIC: City of the Daleks, PROSE: Prisoner of the Daleks) and Davros' chair. (TV: Genesis of the Daleks) Other sources sometimes called these parts of a Dalek casing sensor globes. (PROSE: War of the Daleks, Remembrance of the Daleks) They were colloquially known as bumps (AUDIO: Davros) or Dalek bumps. (COMIC: Four Doctors)

The Sixth Doctor once asserted that "a Dalek can't change its bumps", but then noted that the bumps were actually quite easily replacable, and that it was a rubbish saying. (AUDIO: Davros)

Amount
Generally, the Dalek lower section was composed of fourteen vertical panels which each contained four sense globes, making a total of 56 globes. (TV: The Daleks) The larger Daleks of the New Dalek Paradigm, however, sported only twelve panels, with a vertical column replacing the two back panels, making a total of 48 globes. (TV: Victory of the Daleks)

A reconstructed reconnaissance scout Dalek was distinguished in that it had only three sense globes on each panel of the base unit, making a total of 42. (TV: Resolution) Similarily, the British Proto-Daleks had only three sense globes on each panel — with two bulky middle section rings replacing the upper set of spheres. (COMIC: The Dalek Project)

Appearance
Though these globes were typically arranged in even panels that flared out slightly as they radiating down the body, arrangement was not uniform across all Daleks. The Marine Dalek, for instance, had a different configuration than standard Daleks. (PROSE: War of the Daleks)

Variants and colours
Davros' chair, which appeared as the base unit of a Dalek, had silver sense globes. (TV: Genesis of the Daleks)

The grey Dalek drones, beginning with the first Mark III Travel Machines unveiled by Davros, had black sense globes, (TV: Genesis of the Daleks) as did higher Gold Daleks. (TV: Day of the Daleks) Supreme Daleks of the Supreme Council had gold sense globes. (TV: Planet of the Daleks)

The early silver Daleks, beginning with the Mark I Travel Machine, had blue sense globes, from drones (AUDIO: Guilt, The Daleks et al.) to saucer commanders, to Supreme Daleks (TV: The Dalek Invasion of Earth) and the Emperor's Personal Guard. The Dalek Emperor uniquely had a pair of sense globes which were coloured gold, above a row of black sense globes. (TV: The Evil of the Daleks)

Daleks seen on Exxilon had silver casings with black weapons platforms and sense globes. (TV: Death to the Daleks)

The grey Renegade Dalek drones opposed to Davros had black sense globes, while Supreme Daleks had white globes. (TV: Resurrection of the Daleks, Revelation of the Daleks, Remembrance of the Daleks)

The sense globes of Davros' white Imperial Daleks, originally constructed on Necros, were coloured gold. This included the Special Weapons Dalek and Davros himself, as the Emperor Dalek. (TV: Revelation of the Daleks, Remembrance of the Daleks)

The sense globes of the "bronze" Dalek drones during the Last Great Time War and beyond were coloured gold. (TV: Dalek et al.) This characteristic was shared by the Emperor's Personal Guard, the black Dalek Inquisitor General, the red Supreme Dalek, and the Dalek Emperor himself. (TV: The Parting of the Ways, The Stolen Earth, PROSE: Prisoner of the Daleks) Dalek Sec, a Black Dalek, was distinct in that his sense globes were likewise coloured black. (TV: Army of Ghosts)

Daleks of the Dalek Scientific Division were distinguished by their silver sense globes and domes. (AUDIO: A Thing of Guile)

The sense globes of Daleks disguised as British Army "Ironsides" were coloured in the same shade of green as their casing. (TV: Victory of the Daleks)

The sense globes of four of the New Dalek Paradigm's first five ranks, Supreme, Strategist, Scientist, and Drone, were coloured dark silver. The Eternal Dalek was distinct in that its sensor globes were coloured black. (TV: Victory of the Daleks)

The dark green, robotic Proto-Daleks, which were constructed by the British and Germans as part of the Dalek Project during the First World War, had different base units; the British Proto-Daleks had only three sense globes on each panel of their base unit — with two bulky midsection rings replacing the upper set of spheres, while the German Proto-Daleks' bottom half was adorned with several flat, hexagonal plates in place of the usual sense globes. (COMIC: The Dalek Project)

Function
Sense globes were evidently the instruments of the Dalek self-destruct process; the Dalek named Metaltron ejected all its sense globes to create a field in which it was completely destroyed. (TV: Dalek)

During the 41st century conflict against humanity, a Chief Strategist of the New Dalek Paradigm was connected to its command ship via numerous wires and cables which were fitted to the sense globes of its base unit. They interfaced the Chief Strategist into the computers, and even allowed it to see the battle from the point of view of the drones fighting. (COMIC: The Only Good Dalek)

Similarily, a Black Dalek was connected to Survey Ship Sigma. (COMIC: The Dalek Project)

Individual cases
One Dalek, a recon scout, built itself a new casing in 2019 Yorkshire which had short-range missiles behind each globe. One of these missiles made short work of a tank which sought to destroy the Dalek. (TV: Resolution)

Footage of a Dalek's base unit and sense globes was captured by a British news broadcast during the Battle of Canary Wharf in 2007. (WC: Tardisode 13)

To complete the Empire State Building before the gamma radiation lightning strike hit Earth in 1930, three of the panels with sensor globes of Thay's base unit were removed and attached to the building's mast, as the Dalekanium of the plates was required to attract the gamma strike. In their place, Thay was given crude iron replacement plates. The Tenth Doctor attempted to remove them too late as the lightning struck him, resulting in Dalek-Humans infused with Dalek Sec's altered DNA as well as the Doctor's Time Lord DNA. (TV: Daleks in Manhattan/Evolution of the Daleks)

The bronze "Quasimodo Dalek", which was reconstructed by unfamiliar humans, had a pair of sense globes fitted in place of the luminosity dischargers atop its dome. Additional sense globes were attached to the weapons platform in place of the slats, which were attached to its base unit. (COMIC: The Dalek Project)

Half a casing's worth of sense globes was among the technology removed from a Dalek by a human guerrilla faction on Earth in the 2010s. (AUDIO: The Dalek Transaction)

Within the Dalek Asylum, sensor globes littered the ground among the insane Daleks. Picking one up, Rory Williams mistook it for an egg as a Dalek stuttered. Though Rory attempted to offer it to the Dalek, he soon found that it was saying "exterminate", leading him to promptly escape as the Dalek attempted to kill him. (TV: Asylum of the Daleks)

Within the Dalek City, tickled a Dalek's sense globes while describing the Doctor's TARDIS as "the dog's unmentionables." (TV: The Magician's Apprentice)

A number of sense globes belonging to the Dalek named Rusty, who was captured by the Combined Galactic Resistance, had been lost or damaged by the time he was found by the Twelfth Doctor aboard the Aristotle. (TV: Into the Dalek) Rusty was still in this battered state when the Doctor met him again on Villengard billions of years into the far future. (TV: Twice Upon a Time)

Other references
The Tenth Doctor mistook the roundels within the Twelfth Doctor's version of the TARDIS' control room for "Dalek bumps". It was for this reason that he initially mistook the control room as belonging to the Master's TARDIS. (COMIC: Four Doctors)

Alternatives
The German Proto-Daleks were distinguished in that their base units were adorned with flat, hexagonal plates in place of the usual sensor globes. (COMIC: The Dalek Project)

Behind the scenes
The parodic Comic Relief story The Curse of Fatal Death had its version of the Master outfitted with "Dalek bumps", identified as etheric beam locators, which were placed in such a way that they appeared to give the Master "breasts".

Michelle Gomez confirmed on Twitter that her tickling a nearby Dalek's bumps when referring to the TARDIS as "the dog's unmentionables" was improvised.