Glossary · Regulation

Rating interval

The elapsed period between time comparisons used to calculate a rate.

Explanation

Use actual elapsed time rather than the number of calendar headings when calculating a daily rate. Two readings on consecutive dates need not be exactly 24 hours apart. A rate derived across several days is an interval average; it cannot by itself identify temperature sensitivity, positional error or an intervening disturbance. State the reference and observation precision, and keep the measured error distinct from the calculated rate. This is a documentary-analysis term, not a recommendation to run an unassessed historic chronometer.

Diagram

Schematic: chronometer rate record. Rate schematic: the interval between observations matters as much as the number of seconds gained or lost.

Photographic reference

E. Barthet No. 10 — gimballed box, L2015-3496 — © The Board of Trustees of the Science Museum / Science Museum Group / The Clockmakers’ Museum, CC BY-NC-SA 4.0 as stated by source; commercial-use permission review pending. Official museum or publication source

E. Barthet No. 10 — dial and canister — © The Board of Trustees of the Science Museum / Science Museum Group / The Clockmakers’ Museum, CC BY-NC-SA 4.0 as stated by source; commercial-use permission review pending. Official museum or publication source

E. Barthet No. 10 — exposed movement — © The Board of Trustees of the Science Museum / Science Museum Group / The Clockmakers’ Museum, CC BY-NC-SA 4.0 as stated by source; commercial-use permission review pending. Official museum or publication source

E. Barthet No. 10, L2015-3496: exact chronometer context, not evidence of a recorded rate or a lunar-distance observation.

Cross-references

Nearby regulation terms

Quartz crystal (resonator): A precisely cut piezoelectric crystal that oscillates at a stable frequency when a voltage is applied.
Rate: The daily or per-period gain or loss of a timekeeper relative to true time.
Rate trace: The line a timing machine draws from a watch's ticks.
Rating nut: An adjustment nut that changes a pendulum bob's position to regulate rate in a common gravity-pendulum arrangement.
Reference meridian: The meridian used as the origin for measuring longitude.
Regulating square: A small square used to adjust a regulator from the dial or case.