Timekeeping accuracy
If your watch is not keeping accurate time and is running fast or slow, it is important to first ask a few questions to determine whether the inaccuracy is to be expected or not.
- The first question is whether your watch is a quartz (battery powered) or a mechanical (self-wind or automatic winding). Quartz watches should be highly accurate and should not lose or gain more than a few seconds each month.
- Are you asking too much from your watch? Not all watches are as accurate as your mobile phone.
- Are there any external factors that are causing inaccuracy or the way you are using it?
- How much time is your watch diverting by per day?
Mechanical watches
Mechanical devices assembled with small parts which interconnect and move together, operating with 99% accuracy, are considered to be elite and highly technical and advanced. To put mechanical watches into perspective, if a watch is 99.9% accurate, it would still be off by almost a minute and a half per day. This is commonly seen as unacceptable within the world of luxury watches.
It is therefore important to first question whether you are asking too much of your watch. All high-end luxury mechanical watch movements are graded and tested. Lower-end mechanical movements may not even be graded. In Switzerland, a certification is given to the highest quality of watch movements, tested and graded by a company COSC (Control Officiel Suisse Des Chronometres). Only about 6% of Swiss watches exported have this status. During the 15 day COSC tests, watches are checked with two pieces of data: temperature and the position of the watch. These two external factors should also be taken into account when you are noticing that your watch isn’t keeping accurate time.
To put it into perspective, the minimum requirements for mechanical watches is an average daily rate of -5/+8. This means that the minimum requirements to pass COSC test and to be considered a highly accurate timepiece is to not lose more than 5 seconds per day or gain more than 8 seconds per day.
Watches that are not certified may have even larger loss/gain parameters so it is important to set your expectations accordingly before determining whether you believe your mechanical watch is “accurate” or not.
External Factors
Position
When a watch has been serviced or is built in the factory, it will be regulated. This means that micro-adjustments are made to the balance (the heart of the watch that controls the consistent oscillations ensuring your watch ticks).
When a watch is regulated, it is done so in various positions as a watch is meant to be worn on the wrist. It is done in various positions to account for the fact that a watch on the wrist will operate facing in various directions as the wrist moves, whether this is walking, typing, eating etc. The watch is regulated to compensate for losses and gains in various positions. A regulated and adjusted watch should perform optimally when worn naturally throughout the day.
It is important when checking the accuracy of your watch to ensure it is being tested in various positions, whilst being worn naturally over the course of a few days in order to gain an average reading. If it is laid down on a desk facing upward and tested in only this unnatural position, it may appear that it is gaining or losing considerably more than it has been regulated to for everyday use.
Temperature
Modern, high-end, luxury watch brands have begun utilising materials within their watch movements that are less likely to be affected by slight changes in temperature. Modern, standard watches and older watches are more susceptible to changes in temperature based on their environment. Extreme changes in temperature may have an impact on the dimensions and shapes of some of the internal parts of the movement causing inaccuracies and variances compared to consistent temperatures such as in our service centre and other test environments.
It is important when checking the accuracy to first consider whether it is constantly moving between different extreme temperatures.
Other factors that may cause inaccuracy
Magnetism
If your watch has been exposed to a strong enough magnetic field, it may cause the balance spring to become magnetised. This causes the coiled spring to stick together and shortens the rotation of the balance wheel which increases the rate at which your watch runs.
Impact
As watches are almost an extension of our bodies, we often don’t notice that we’re wearing them. Sometimes they are so comfortable and a consistent part of our lives that it’s more noticeable when we’re not wearing our watch. This can sometimes mean that our watches can get knocked and beaten around a little more than we’d expect. Bumping it into a doorframe or even dropping it off the bedside table could be enough to have a knock-on effect within the watch movement causing coiled springs to become tangled or other parts to become shifted or broken. If this is the case, then your watch should be seen by an expert watchmaker before any further damage can happen.
How to test the accuracy of your watch at home
In our service centre, we have electronic devices that are specifically calibrated and designed to check the accuracy of mechanical watches in various positions, allowing us to regulate and adjust them accordingly. We appreciate that, at home, you will not have these machines so the results of your home tests will not be as accurate as ours, however it can provide a good baseline from which to determine whether there are any faults.
- Fully wind your watch up so it has as much power stored as possible.
- Set your watch to time by comparing it to a device which sets by radio control or the internet such as a smart phone. If you can, set it to the exact second by waiting for your watch’s second hand to reach 12 and then pull out the crown so your watch stops. Set your watch to the minute after that which is displayed on your other device and as soon as your device flips over to the new minute, start your watch again. This way your watch and your smart device will be perfectly synchronised. It is important to note that not all seconds hands on watches will stop when the crown is pulled out so make a note of the exact difference in seconds between your watch and the device you’re comparing it to.
- Wear your watch naturally so it can experience being put in several different positions. If you can’t wear your watch, alternate its position on a desk every few hours.
- We would then recommend testing the accuracy of your watch after 24-hours and then again after 48-hours.
Once this test has been completed, compare it to the following table to see whether your watch is within tolerance.
Please also note that this table is a guide and some brands may in fact be better or worse than shown below. Worn parts may also be a factor in how your watch performs.
Seconds per day
Type of watch
Worst case
Typical
Excellent
Vintage
+/- 60
+/- 20
+/- 10
Modern non-certified
+/- 20
+/- 10
+/- 5
Modern certified
+/-6
+/- 3
+/- 1
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Other Useful Information
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