Caesium atomic clock no. Hp5071a by Hewlett Packard

Record summary

Held and catalogued by Royal Museums Greenwich (object number ZBA2599), this is a caesium atomic clock by Hewlett Packard, dated 1991. The Atlas places it in the Mechanical Renaissance period (1990 – 2010) of its Clocks collection. Materials and techniques recorded by the source: metal; plastic. Recorded dimensions: Overall: 135 x 425 x 525 mm. The record is illustrated with 1 photograph.

Assembled from the source record's structured fields. Dates and attributions are given as the source states them; where a field is missing the Atlas leaves it blank rather than estimating.

Catalogue description

Atlas type guide

Quartz, atomic and electronic time standards

In 1927 Warren Marrison and J. W. Horton at Bell Telephone Laboratories built the first quartz clock, which used the piezoelectric vibration of a quartz crystal as its oscillator. Quartz clocks replaced pendulum regulators in observatories in the 1930s and 1940s and revealed irregularities in the Earth's rotation. In 1955 Louis Essen and Jack Parry at the National Physical Laboratory in Britain operated the first practical caesium atomic clock; in 1967 the SI second was redefined in terms of the caesium-133 transition.

Atomic and quartz standards are distributed by radio time signals, telephone 'speaking clocks', and today by satellite navigation and network time protocols. Objects in this group — oscillators, frequency dividers, receivers, master clocks — document the transition from mechanical to electronic timekeeping.

General guidance written by the Atlas editors about this kind of object. It is not a statement about this particular piece; for that, rely on the source record above and on physical examination.

Read next:The Quartz Revolution era