I recently purchased a Nivada Grenchen Antarctic Chronometer which is keeping excellent time but not any better time than any of my RR watches. Is your typical RR pocket watch essentially a chronometer?

From all definitions I've been able to find, the answer would be 'yes', as they all say it refers to extremely accurate timepieces designed for extremely accurate time keeping.

That said, I also found THIS definition that took it a step further:

"A chronometer is a clock designed to have sufficient long-term accuracy that it can be used as a portable time standard on a vehicle, usually in order to determine longitude by means of celestial navigation. Today only timepieces certified by the COSC may use the word 'Chronometer' on them."
http://www.wordiq.com/definition/Chronometer

Regards! Mark

So without the COSC certification you just don't have a chronometer no matter how accurate the watch may be?

I guess so, at least that's what the website claims. Is yours certified?

The definition for that is essentially the same as 'chronometer':

"chronograph [ˈkrɒnəˌgrɑːf -ˌgræf ˈkrəʊnə-]
n
1. (Miscellaneous Technologies / Horology) an accurate instrument for recording small intervals of time
2. (Miscellaneous Technologies / Horology) any timepiece, esp a wristwatch designed for maximum accuracy"

So, mine is just capable of breaking down the time in smaller intervals with a stop watch function, and yet has the same secondary definition as a chronometer.

Regards! Mark

It's marked 'OFFICIALLY CERTIFIED CHRONOMETRE' on the dial. I suppose you could have had a chronometer that wouldn't have qualified as a RR watch.

dana

Here is yet other definitions which I think eliminates RailRoad Pocketwatches....


#1
Britannica Concise Encyclopedia:

Chronometer:


Mechanical timekeeping device of great accuracy, particularly one used for determining longitude (see latitude and longitude) at sea. Early weight- and pendulum-driven clocks were inaccurate because of friction and temperature changes and could not be used at sea because of the ship's motion. In 1735 John Harrison invented and constructed the first of four practical marine timekeepers. The modern marine chronometer is suspended to remain horizontal whatever the inclination of the ship and differs in parts of its mechanism from the ordinary watch. A chronometer may provide timekeeping accurate to within 0.1 second per day. See also Ferdinand Berthoud.
For more information on chronometer, visit Britannica.com.


#2
McGraw-Hill Science & Technology Encyclopedia:

Chronometer:

A large, strongly built watch especially designed for precise timekeeping on ships at sea. The name is sometimes loosely applied to any fine watch.

The features that distinguish a chronometer from a watch are (1) a heavy balance wheel, the axis of which is kept always vertical; (2) a balance spring wound in cylindrical shape, instead of a nearly flat helix; (3) a special escapement; and (4) a fusee, by means of which the power of the mainspring is made to work through a lever arm of continuously changing length, being shortest when the spring is tightly wound and longest when it has run down, thus regulating the transmitted power so that it is approximately constant at all times.

Oceangoing ships during a voyage formerly relied completely on chronometers keeping Greenwich mean time as a means for determining longitude. The broadcasting of radio time signals that became widespread in the decade 1920–1930 has made Greenwich mean time available to mariners at almost any time of day, and chronometers are no longer indispensable for determining longitude at sea. See also Clock.

Regards,

Jerry

Then, is my wrist watch truly a chronometer?

If I remember correctly, the railroad standard was +/- 30 seconds per week measured against a standard clock. Chronometers are clocks/watches that don't necessarily do this. What they do is to keep the rate of change in each position within =/-10 or so seconds a day. So, a chronometer could be off as much as 70 seconds per week in a given position exceeding the railroad standard. I think the standard is a max of =/-10 seconds in each position but I may be off a bit.

Remember the primary purpose of a chronometer was a navigational one where rate of change was critical to determining a nautical position. But, I don't think the standard necessarily means the watch will be an accurate time keeper.

Believe I saw -4 to +6 seconds/day as the COSC standard as well as adjustments for temperatures and positions.

Accuracy is a secondary requirement for a chronometer rating. The primary requirement is repeatable daily timekeeping ,in other words , the ability to repeatedly run day after day gaining or losing at the same rate each day, so that a calculation added or subtracted from or to the chronometers reading would give exact Greenwich time so as to calculate longitude,thereby fixing the ships exact position.It is less important to state the exact time on a given day ,than to take exactly the same time to run for 24 hours ,plus or minus the same factor of rating,day after day after day. That way a minor calculation gives you the exact time -and thereby your location in relation to land or reefs etc.

add this from Wickepedia to help confuse or clarify the air British mariners kept at least one chronometer on GMT in order to calculate their longitude from the Greenwich meridian, which was by convention considered to have longitude zero degrees (this convention was internationally adopted in the International Meridian Conference of 1884). Note that the synchronization of the chronometer on GMT did not affect shipboard time itself, which was still solar time

I also think that the device must be a mechanical movement with escapement, so no quartz technology would qualify to be a true chronometer.

Wild! My Seiko Quartz "Chronograph"? has not deviated for two years.