The spring writing drive runs until the end of the month: pick a stub and help finish it.
\n\nthe open reference on timekeeping that anyone can edit.
\n12,480 articles, written by their readers
\n \nA water clock measures time by the regulated flow of liquid into or out of a vessel. Together with the sundial it is among the oldest timekeeping instruments, and it stayed in use where the sky was overcast or the hour fell at night. Outflow clocks are marked on the inside of a draining bowl; inflow clocks read a float that rises in a second vessel fed at a steady rate.
\nLater builders added gear trains, bells and moving figures, and a constant-level tank to keep the pressure even. The instrument was only displaced by the verge escapement and, later, the pendulum. (more...)
\n \nFrom chronoskin, the open reference on timekeeping
\n\n \n\nFor the sinking-bowl timer used to share out irrigation turns, see Water clock (irrigation).
\nA water clock is an instrument that measures time by the regulated flow of liquid into or out of a vessel, where the amount is then read against a scale. With the sundial it is among the oldest instruments for telling the hour, and unlike the sundial it works indoors, under cloud and at night.[1]
\nThe simplest form is a bowl with a small hole near its base. Makers soon found that the flow slows as the level falls, and much of the later history of the instrument is the search for an even rate.[2]
\n\nContents [hide]
\nAn outflow clock is a vessel that drains through a narrow opening. Hours are marked on its inner wall, and the wall is often sloped so that equal drops in level stand for nearly equal times. A formula of the form t = k * sqrt(h) describes the emptying of a straight-sided vessel.
An inflow clock collects the water in a second, straight-sided vessel in which a float carries a pointer. Because the receiving vessel does not affect the rate, the scale can be evenly divided, provided the supply is steady. The usual remedies were:
\nThis section needs more sources. Figures below come from a single modern reconstruction. Help improve it by adding measurements from published tests.
\nTemperature changes the thickness of water and so the rate of flow; a clock set in summer runs slow in winter. Tests on modern replicas give the figures below.[3]
\n| Form | Regulator | Run time (h) | Error per day (min) |
|---|---|---|---|
| Plain outflow bowl | None | 6 | 45 |
| Sloped outflow vessel | Wall profile | 12 | 20 |
| Inflow with overflow tank | Constant head | 24 | 12 |
| Inflow with float valve | Feedback valve | 24 | 10 |
Categories: Timekeeping instruments | Clocks | Ancient inventions | Hydraulic devices
\nFrom chronoskin, the open reference on timekeeping
\n\nLegend: (cur) = difference with the current version, (last) = difference with the version before, m = minor edit. Sizes are in bytes.
\n \n| Compare | Date | Editor | Size | Change | Summary |
|---|---|---|---|---|---|
| (cur) (last) | 09:14, 4 March 2007 | Halvard (talk) | 8,412 | +236 | Accuracy: added replica trial figures unchecked |
| (cur) (last) | 21:50, 2 March 2007 | Ines Corbel (talk) | 8,176 | +12 | m spelling checked |
| (cur) (last) | 18:03, 2 March 2007 | Tamsin R (talk) | 8,164 | -1,940 | removed the section on float valves reverted |
| (cur) (last) | 11:27, 27 February 2007 | Oduya (talk) | 10,104 | +1,318 | Inflow clocks: constant-head tank, with a source checked |
| (cur) (last) | 08:41, 19 February 2007 | Halvard (talk) | 8,786 | +402 | fact box, picture caption checked |
| (cur) (last) | 16:12, 3 February 2007 | 81.0.2.117 (talk) | 8,384 | -58 | m tidied the see also list checked |
| (cur) (last) | 22:35, 28 January 2007 | Ines Corbel (talk) | 8,442 | +2,077 | rewrote the lead and the principle section checked |
| (cur) (last) | 14:06, 11 December 2006 | Oduya (talk) | 6,365 | +6,365 | new page, moved from the workshop |
From chronoskin, the open reference on timekeeping
\n\nYou are editing an old version of this section. If you save it, the two changes made since then will be lost. Compare the versions first.
\nYour edit was not saved. The summary is empty, and this page asks for one. Add a line that says what you changed and save again.
\nNothing to preview yet
\nYou have not asked for a preview of this edit. A preview shows the section as readers will see it, before anything is saved.
\n Show preview\nYou are about to delete this page together with all 37 versions of its history. Sysops can restore it; readers will see a red link.
\n \n