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Reviews > Electronic Devices > Watches > Timex WS4 Watch > Test Report by Roger Caffin
|Initial Report 8-July-2009|
I started bushwalking at 14 and took up rock climbing at University with the girl who became my wife and my permanent walking partner. Ski touring and canyoning followed. Winter and summer, we prefer long hard trips by ourselves: about a week in Australia, up to three months in Europe/UK. We prefer fast and light in unfrequented trackless country. We would be out walking, skiing or snowshoeing for at least three months a year. We have now moved to lightweight gear, much to our backs' relief. I designed and made much of our lightweight gear myself.
I am also the maintainer of the Australian aus.bushwalking FAQ web site www.bushwalking.org.au/FAQ/.
My watch says Morning Tea Time
|Year of manufacture:||2009 (assumed)|
|Country of manufacture:||China|
|Weights (measured)||Watch: 63 g (1.80 oz)
Strap: 25 g (0.80 oz)
Neck cord: 9 g (0.32 oz)
|Dimensions||Width: 53 mm (2.09")
Length: 68 mm (2.68")
Thickness (body): 17 mm (0.67")
Height above deck: 28 mm 1.10")
|Water Resistance:||Claimed 50 m, but see below for what this means|
This is a digital watch with the standard Barometer/Altimeter and Compass features, along with the common extra features such as dual time zones, chronometer, data logging, etc. (With the current state of the art in integrated circuits, these extra functions are excessively easy to add to a watch, whether they are needed or not.) It has the usual four control buttons plus an 'Indiglo' button for the back illumination. Where it starts to deviate from a 'standard' watch is the size of the unit, and I will return to this point shortly. The model number 'WS4' apparently means 'Wide Screen with 4 functions' - all true.
The unit comes with a glossy (laminated) fold-out quick reference guide with brief instructions in English, French and Spanish, and a compact (and thick) instruction guide in the same languages. The latter fits into the box base on the watch stand. All the glossy fold-out guide covers is some esoteric features of the altimeter - mainly how to use the altitude alarm feature. It seems that whoever wrote the main manual forgot to mention these features - or they were added to the software after the manual was printed
The Timex web site is rather confused when it comes to describing the strap. It variously describes the strap as 'Durable Resin Strap', 'Black Resin strap' and 'Buckle/Clasp Type: Buckle', and reading the other Test Reports for this watch will show that this is roughly correct. However, the unit I received has a strap made of heavy elastic some 30 mm (1.2") wide, held at one end with about 40 mm (1.8") of hook&loop fastening and at the other end by a moderately complex stainless steel adjustable buckle. This strap does not appear on the obvious WS4 web page, but delving deeper into the web site I found an FAQ page which said this: 'Comfortable and durable rubber strap or XL Elastic Fast Wrap to fit outside of performance gear'. Unfortunately it also said 'Unless you have the WS4 with an XL elastic strap (which can be removed completely), the strap on the WS4 was not designed to be removed and replaced. If your strap breaks, you can contact Timex Customer Service at 800-448-4639 or email@example.com', so for the present I am stuck with an XL wrist strap which is unusable for ordinary walking.
The web site shows the black version as having jungle green buttons. My unit has bright orange buttons. I suspect that the change in colour may be associated with the change in the wrist strap.
In one place on the Timex web site the specifications claim 'Dependable water resistance to 50m' and in another place 'Water Resistant 50 M'. On the TimexExpedition web site (yes, there are two different Timex web sites) there is very little in the way of specifications for the WS4 that I could find, but there is an FAQ page with some interesting comments. My own feeling is that many people would not discover the TimexExpedition web site or the FAQ page for the WS4 when starting from the Timex web site.
Anyhow, I was quite enthused when I first read (on the Timex web site) that the watch was water resistant to 50 m - it meant I could use it swimming rivers and abseiling wet canyons - things we often do on some trips. However, reading the FAQ page I discovered this:
'We do not recommend swimming with your WS4. The WS4 is 50 meter water resistant, and the general rule of thumb for any watch is: 30 meter can be safely splashed; 50 meters is safe in a shower; 100 meters is safe in the pool; and 200 meters is safe for snorkeling or light diving.'
My reaction to this discovery was fairly severe and I was ready to accuse the company of deceiving me. However, fellow BGT members pointed out that the term 'water resistant' is an industry term and is actually defined by an ISO Standard. (My thanks to these guys.) I don't have access to the text of the ISO standard, so I will quote Wikipedia instead.
The international standard 'ISO 2281 Horology -- Water-resistant watches' defines the water resistance of watches. This standard was only designed for watches intended for ordinary daily use and are resistant to water during exercises such as swimming for a short period. They may be used under conditions where water pressure and temperature vary. However, whether they bear an additional indication of overpressure or not, they are not intended for submarine diving.
The Wikipedia page goes on the explain that testing for 'water resistant' is done by immersing the watch to a depth of 10 cm (about 4 inches) for 1 hour. Where a depth is quoted, the watch is also tested once at that water pressure for 10 minutes.
In addition, the ISO standard says that a watch rated as 'water resistant 50 m' should be
Suitable for swimming, white water rafting, no snorkeling water related work, and fishing. Wikipedia also says ISO 2281 compliant watches are designed for everyday life and must be water resistant during exercises such as swimming for a short period..
As far as I can see, the ISO standards do not use the common term 'waterproof' at all.
So I am willing to accept that Timex are simply following 'industry standards' here, but ...
Did I mention that this thing is huge? The dimensions are in the table above, but it is not until I held the watch in my hand that I realised that plasma TV screens are not the only thing which come in an super-size category. Once again, I have to say that (in my opinion so far) the watch seems more designed for street machismo wearing than for real use when out bushwalking. I say this because a thing this size really would get in my way when fighting my way through thick scrub. But we will wait and see for the Field Report to see.
There seem to be four small hex head bolts on the front of the watch. These are clearly visible in the lead photo. However, despite my best efforts, these don't seem to do anything and don't seem to rotate. One is left to wonder whether they are anything more than pseudo-macho ornamentation.
The 'wide screen' display is certainly large. It has a small analog clock face at the top left hand corner which does double duty as the analog compass display, although the resolution is low. It has a dot matrix digital display at the top right hand corner: this is arguably the 'main' display, and very readable. In compass mode it is limited to displaying the cardinal points rather than degrees, which I found a little strange. At the bottom left hand corner there is a temperature display and a set of weather symbols of the usual format - clouds, sun, rain etc. In compass mode the actual bearing in degrees is shown here. At the bottom right hand corner there is a set of seven-segment number which are used for secondary displays such as Altitude in Time mode, date in Altitude mode and setting the altitude reference points. Great care must be taken when reading these numbers as they are very narrow and some characters are hard to interpret. In particular, the plus and minus signs in altitude reference mode are almost incomprehensible at first. One gets used to them after a while, but I did have one of my altitude references set to -188 m (rather than +188 m) for a while.
Finally, at the bottom right hand corner on the metal surround there are four little black embossed logos. They do occupy space which could have been used by the LCD display. As far as I can see at this stage, they serve no useful or functional purpose. They seem to be just fancy trim.
I tried to adjust the elastic strap to fit my wrist, but this was not possible. Even at the tightest setting it slid up my arm. Then I found the bit in the FAQ about the strap being for use with 'performance clothing', but my 'performance clothing' is never that bulky. (Think single-layer Taslan or single-layer Lycra.) The strap just manages to hold at my wrist when I am wearing a wet-suit (albeit rather loosely), but I can't use the watch in the water as the '50 m water resistant' specification does not mean the watch can actually be used in water. With the strap fully extended I can get both wrists into the strap quite easily - see photo to the right. (No, this is not a bondage item!) 'XL' is certainly correct; 'usable' is less certain.
The unit came with a fairly robust neck loop which can replace the wrist strap. It is secured to the watch with a short bit of hook&loop fastening. I did notice that the stuff tended to peel open rather easily (a Chinese brand?), and how reliable the attachment might be in the field is definitely open to question.
I spent some time setting the watch up to my requirements - metric units, local altitude, etc. This required reading the small instruction manual. The first problem was that the font was so small I had to take all my glasses off before I could read it (I am short-sighted). However, the printing was of good quality. The second problem was that the instructions are not always easy to follow, and do seem to leave a few steps out in places.
The instructions for setting Time and Date are on page 14 (and page 11) of the little manual. Technically the instructions are correct, but they are a bit confusing. Before reaching the actual time and date display the user must select 'Time1' or 'Time2' and press 'Mode'. This is not obvious at first, and I found it rather puzzling. Careful reading of the fine print shows that the manual does cover this, but the casual reader is likely to miss it.
The instructions for setting the altitude to match the local environment (page 15) are even more confusing. On most watches the Start (Up, + or whatever) button increases the displayed number; on this watch it does do this but only for one digit at a time. It is necessary to advance from the hundreds to the tens and to the units (etc) by pressing the Mode button. Further, unless the STOP button is pressed at the end the whole process will be largely ignored. I got very confused here for a while. There is a note about this in the FAQ page at the web site.
Calibrating the compass is essential before use, and this uses the 'normal' two rotations of the watch. After this the declination can be set. All this went very smoothly, but the result was not good. In the end it turned out that my steel filing cabinets were distorting the local magnetic field! I moved into a clear space and redid the calibration successfully. The manual does not explain anywhere that the resulting display is for 'True North', not 'Magnetic North'. This might confuse a novice. However, this does not cover the effect of tilting the watch, which has been found to cause major errors in other watches. This aspect will be covered in the Field Report.
The alarm works: it beeps (at a high pitch) and flashes the blue display back-light a number of times. It is a pity I can barely hear the alarm, although my wife says she can. She says I have lost the high end of my hearing spectrum. That happens with age, but it does make the choice of a very high pitch questionable. However, given the size of the piezo disk inside the watch, the high pitch may be unavoidable.
The manual contains several quotes from a well-known mountaineer, but such things are just common commercial testimonials for which the vendor pays the 'name' money. In my experience such paid 'testimonials' mean absolutely nothing. Even Tiger Woods sells (or did sell) his name to all sorts of companies for testimonials.
Field Report - 6-March-2010
It would be easy just to say 'I took the watch on several trips and it told me the time', so I thought I would include a bit of testing I did at home as well. For this testing I used the WS4 watch, an 'other' watch which I have previously tested for BackpackGearTest, and the USA time web site at www.nist.gov (National Institute of Standards). Since the XL elastic strap provided was useless around my wrist I used the neck loop instead, and either carried the watch hanging from my neck or in a chest pocket.
That said, I did take the WS4 watch on the following trips, and it did tell the time and altitude quite well. On some of the trips I also took the 'other' watch as well.
The watch possesses many little extra features each of which might appeal to someone. However, most of these extras are of no real use to me, so I have concentrated on the areas which are of interest to me. Some of the extras may be covered by other reviewers. Sometimes I suspect the extras are only there because the microprocessor chip and memory used had room for them - can't leave waste space you know!
I had no trouble reading the display for time or altitude. On the other, I only really looked at the time and altitude figures: I generally ignored the 'analog' watch display and the temperature and weather displays. Actually, by now I think the 'analog' watch display is wasted space: it is actually harder to comprehend than the numbers.
I did try using the backlight to check on the time during the night. The biggest problem was finding the button for the light. The first time I activated it I found that I had the watch upside down, so I had to turn it around and try again. Maybe I am a bit clumsy at 2 am. But anyhow, I was able to read the time using the backlight. That said, the subsequent times I simply grabbed my headlight, muffled the output with my fingers, and used it to find the watch and read the time.
In the past I have found the compass section of digital watches to be both power-hungry and rather unreliable. I note that this watch does turn the compass off after 30 seconds, to save power. In some cases I found that 30 seconds was quite long enough, but not always. It was enough if all I wanted was a quick check on North.
As for the accuracy of the watch compass - that is not so good. My experience has been that digital watch compasses are very sensitive to any tilt or roll. Unlike a mechanical compass, where I can see the needle and verify that it is free to swing (and correct as needed), watches do not allow this sort of check. So I did some laboratory measurements to see how badly this watch is affected by tilt and roll. I have included some technical information in a section below about the sensors used for magnetic compasses as well.
I use the term Tilt to describe the sort of rotation experienced when my wrist is rotated. I use the term Roll to describe what happens when my arm flaps up and down. It is at right angles to Tilt.
Ideally one would attach the watch to some sort of goniometer to rotate it at various amounts of tilt and roll, to see whether the compass readout changes. I could use the dividing head on the mill in my workshop for this, but it is a huge lump of steel with its own magnetic field - not such a good idea. So I used a simple plastic goniometer I had made up instead. This is illustrated in the photo to the right. The small dimples at the left hand end of the white tube are aligned with the sheet plastic end stop: they are quite precise steps of 4.5 degrees (marked with the dividing head on my mill). The green support base cradles the white tube so it can rotate smoothly, while the black bungee cord keeps the tube in place and from slipping. With the watch mounted on the tube as shown in the photo here, rotating the white tube (as in rotating my arm) changes the Tilt of the watch. Mounting the watch on the white tube at right angles to how it is in the photo gives Roll. The small spirit level (from a laboratory optical bench) was used to get zero Tilt while measuring Roll and vice versa.
I aligned the rig to point roughly North and roughly East, taking Tilt and Roll measurements at each. The results are shown to the left.
Consider first the red line. This shows the effect of tilt (rotating my wrist) when the compass is indicating approximately North. In fact, there is very little effect at all in one direction (rotating backwards, or towards me), and little effect in the opposite direction for a little while. This is very good, and means that the compass could give useful results under these conditions. The abrupt change in readout at about +20 degrees is not unexpected or unreasonable, and is due to the prevailing tilt in the Earth's magnetic field here in Sydney. It is about 64 degrees (very steep), so when the watch is tilted about 20 degrees the poor thing is almost at right angles to the Earth's magnetic field! Of course, one would not attempt to use a compass which was tilted over that much anyhow.
However, now consider the brown line: the effect of Tilt on the compass when it is indication East. Here the results are not good. There is a smooth variation in the indicated direction as the watch is tilted. This shows about 1.8 degrees error per degree of tilt. As I cannot be sure my watch is horizontal to better than (about) ±5 degrees in the field, this gives an error range of about ±9 degrees, which is more than I am willing to accept. (Yes, I can read a compass to within 1 degree in the field, although I do not normally need to.)
The two blue curves give the results for rotation in the other axis - Roll. In effect they are similar to the results for Tilt, although the sensitivity for Roll N is higher, at 2.3 degrees error per degree of roll. The similarity is reasonable since the compass system (typically) relies on two magnetic field sensors at right angles to each other.
It is true that the extreme cases or error here are ridiculous: one would simply not attempt to use any compass when tilted over that much. My concern is with the lower angles of tilt and roll: there is an effect, and one cannot easily tell whether the watch is properly aligned horizontally or not. As mentioned above, at least with a mechanical compass I can see whether the needle is free to swing.
My conclusion here is that the digital compass part of this watch is not sufficiently reliable for serious use. I will continue to rely on my traditional mechanical compass - which has the advantage that it needs no batteries and won't stop working if I use it all day.
Modern digital watches are a far cry from the earlier analog balance wheel and escapement systems, and even a cheap digital watch can be more accurate. But how accurate is a good question. As mentioned above I used NIST to provide a reliable 'absolute' time, and I did this for the two months covered by the Field Report.
For the more technically minded, I must point out that reading NIST time involves the use of the Internet, and the Internet service has a variable delay in response due to network traffic. Typically the uncertainty in reading NIST time is of the order of 0.5 - 1.0 sec according to the sync protocol used, but there have been times when this 'uncertainty' got larger. This does not normally happen and was mostly due to my firewall waiting for me to permit the traffic, but single point blips in the results can be explained by this variation.
Two curves will be seen in the graph: the blue one is for the WS4 watch and the red one is for the 'Other' watch. In looking at these results it is important to remember that the watch cannot be read to better than ±1 sec, and the NIST timekeeping I used was being read to the same accuracy. That means that a variation of ±2 sec in any single result may be expected. However, over a long period such as 2 months, any drift becomes very clear.
As may be seen from the graph, both of my watches drifted with respect to NIST time. The drift for the WS4 was about -2.30 seconds per week. For the 'Other' watch it was about +3.92 seconds per week. One could worry about this, but these are not 'chronometers' meant for ultra-precision. It suffices to have some rough idea of the drift.
I was not able to measure this in absolute terms with readily available equipment, for two reasons. The lack of a precision pressure gauge was one, but far more significant was the way the weather fluctuates from day to day - in any location. Variable weather means variable barometric pressure, which gives a perception of varying altitude. So all I can say is that the altitude readings I took at known positions on the trips done during this period seemed fairly reasonable, even if not 'spot-on'. Instead I chose to track the difference between the WS4 watch and the 'other' watch mentioned above.
Both the WS4 watch and the 'other' watch appear to just measure and present the barometric pressure and altitude. If correct, this is good. A third watch I have tested had software which tried to differentiate between variations in pressure due to weather and variations due to genuine changes in altitude. That is an impossible task. Needless to say the software used in that watch was hopeless, and the calibration or altitude drifted continuously.
In the graphs to the right I have shown the pressures indicated by the two watch altimeters on two different trips. Obviously, the red and blue lines (left hand scales) show that the two watches tracked moderately well. However, the green lines (right hand scales) show the offset between the two watches, and clearly they did not track exactly. Granted that the offset between the two watches, and the shifts in the offset, were not that great, but my question is why did even these shifts happen? The silicon sensors do not have any significant hysteresis, so I am puzzled. When I am puzzled my trust level goes down.
The next graph (left) shows the offset between the two watch altimeters over the two month Field Test period. Both watches were set to 188 m at the start (the altitude of my house) before I went on a walking trip which went up to ~1200 m or 4,000'. The dashed part of the line was the period of the trip. After the trip there was a 32 m (105') offset between the two. This offset persisted until the day before I went over Parr South, when it reduced to a much smaller value. The little jiggles correspond to the left-hand graph of the two above. Around the 13th and 14th we had a series of summer storms, when the weather went from very hot to pouring rain once or twice a day. There is a noticeable increase in offset there. Then on the 20th we went over Mt Townsend, and another shift in the offset occurred. In between these 'events' the offset seems fairly stable.
The stable regions mostly correspond to the watches sitting on my desk at home. It is good that my house does not go up and down! However, I do expect that the pressure should show some changes over time as Sydney weather has been rather volatile. The 'Other' watch showed daily fluctuations which did correspond to the passage of various fronts. The WS4 watch sat resolutely on 166 m for most of the time, despite the weather changes. This suggests that either it cannot respond to small changes in pressure or that it has some sort of adaptive software which tries to cancel out weather changes. I find no mention of this in the manual.
Pursuing this I note that on page 18 the manual explicitly says that changes due to the weather will change the apparent altitude. On the other hand, the manual claims that the barometer part of the watch will display both current barometric pressure and the corrected sea level pressure. Just how any barometer can be expected to know what the real altitude is to be able to do this is beyond me. I don't believe it.
If we discount the idea of a software 'feature', the obvious question is which watch was responsible for the odd shifts. That is hard to say absolutely without a reliable measure of pressure. However, the 'Other' watch did display shifts which corresponded to the passage of weather changes, while the WS4 did not. This leaves me trusting the 'Other' watch rather than the WS4. All in all, I have to put the WS4 into the 'less reliable' role - unless it has a 'weather-compensation' feature.
Equally interesting is the resolution displayed by the two watches. Both display height to 1 m, and the 'Other' watch appears to be sensitive to a 1 m shift. (I have checked this.) However the WS4 watch seems to only display far larger shifts - of the order of 5 m. This would have to be a 'feature' of the electronics and the software inside the watch. That said, there was one occasion when the altitude shifted from 166 m to 165 m - a shift of just 1 m. Odd. Does any of this really matter? I think not, as variations in barometric pressure due to the weather create much larger shifts in apparent altitude.
The basic oscillator and time-keeping circuits in a watch do not take a lot of power. By themselves they might run for many years on a single battery. However, the pressure sensor (for barometer and altimeter) takes more power, and the magnetic sensors (for compass) take a lot of power. The manual mentions that the compass display only runs for a short while (30 sec) before turning off. Both sensors are 'sampled': the data is only refreshed every so often (every few seconds I think). In between samples the power to the sensors is turned off to conserve the batteries.
What the manual does not mention is that the altitude display only lasts for roughly 3 minutes, after which the watch reverts to the Time display. I am slightly puzzled about this as the Time display which follows does still show the altitude. It may be (I do not know) that the updating of the altitude is then far less frequent. After all, it is unlikely that I would ever need to know the altitude on a second by second basis! The manual makes no mention of this behaviour. Perhaps it is just a software 'feature' which some software designer though appropriate?
The altimeter display actually seriously annoyed my in the field - or perhaps I should say the person who designed the software annoyed me. Most watches allow the user to record the peak altitude reached since the last reset, and the shift in altitude. For a few people this might be interesting. The person who designed the software in the WS4 made the ridiculous decision that, when one selects 'altitude', the watch should first display the peak altitude for several seconds, then the altitude shift again for several seconds, and only after those two does one get to see the current altitude. Frankly, I found this irritating every time I had to sit there and wait for the watch to roll through those totally irrelevant bits of useless information before telling me what I wanted to know: the current altitude. This is bad design.
The watch has an algorithm in it which uses the rate of pressure change to try to predict the weather for the next 6 - 12 hours. There are a few little icons to show the result: sun, clouds, rain, etc. The manual mentions that the user may have to 'calibrate' the watch for weather, which I think means altering the thresholds between the several predicted states. Sydney weather is sufficiently unpredictable that I have not bothered trying to improve on the default values. The results of the algorithm seemed roughly in accordance with the weather, but I can usually make as good a prediction by looking out the window or up at the sky. Since the Weather Bureau never gets it entirely right either, I am not surprised at the limitations in the watch.
As noted in the Initial Report section, the XL elastic strap supplied was useless for me. I did try doing the strap up to the tightest possible setting, as shown here again, but that still left it too loose to be usable around my wrist.
I contacted Timex Customer Service about this. Finding an email address for Customer Service on the Timex web site was not the easiest thing to do, but it was there - under Website Help at the bottom of the Outdoors screen in a faint grey. Not what I would call eager to be found.
I received a reply within an hour on 14-January, which was impressive. The reply was:
'Thank you for your inquiry. You can call us at 1-800-448-4639 to order a replacement band for your watch. The cost will be $8.00-$12.00, plus any applicable tax. Please have your watch with you when you call.This was encouraging - perhaps. The manual does state however that the elastic strap cannot be changed by the customer. Inspection of the watch showed that was not true: all it needed was a small Phillips head screw-driver.
Making trans-Atlantic phone calls at midnight (there is a large time zone shift between Australia and the USA) is not my favoured pastime, so I asked whether it could be done by email. I received a reply within one day from the same person giving me an email contact. So far so good.
I emailed the contact on 19-Jan-2010 explaining the problem. The email did not bounce, but it did not get me a reply either. So I emailed the same contact again on 26-Jan-2010 and got a reply the next day. This referred me to the Australian distributor for Timex, and the Spare Parts Manager for the distributor emailed me advising that a replacement strap was available for AU$40. All in all, I thought the service provided was quite good so far, although the inflation from US$8 - 12 to AU$40 was a bit steep. This inflation over the USA prices seems to be common in Australian retail.
Up to this point I had not mentioned BackpackGearTest.org at all: I was just a customer. Not wishing to spend $40 for a strap I was unlikely to ever use I went back to Timex in America on 2/2/2010 to see if they would be willing to provide the strap for free as part of the field test agreement. I had heard nothing by 8/2/1010, so I tried again that day. For some reason it seems I always have to send such emails twice before they get 'seen'. However, I then got a reply and my contact at Timex did offer to send me a standard wrist strap at no charge around the end of February. At present I am still waiting to see if it arrives.
In summary then: dealing with any large corporation like this seems to always require a lot of persistence by the customer. I guess that is inevitable. In this case however both the company and its agents were fairly responsive and helpful, although the bottom line has yet to arrive.
Magnetic Field Sensors - Technical
Mentioned above is the excessive sensitivity of the compass in the watch to tilt in any direction. This is a known problem for 2-axis magnetic sensors acting in a 3-D magnetic field. While much research1 has been done on handling this problem, it remains likely (in my opinion) that only a full 3-axis magnetic sensor can really be trusted to indicate north reliably in a real planetary magnetic field with dip (such as Earth). My opinion seems to be shared by some vendors.
Two different sorts of magnetic field sensors are available for miniature integrated units. One sort uses an amorphous magnetic alloy whose resistance is a function of the surrounding magnetic field; the other sort uses an enhanced Hall-effect sensor. The Hall-effect sensor (eg from AKM Semiconductors) is the older form, but is bulky due to the need for magnetic flux concentrators to surround the sensors. (These can be as simple as lumps of soft iron.) The magneto-resistive sensor used to be expensive, but by 2009 the price for a 3-axis unit had dropped to below US$1, going as low as US$0.50 in 2010. Manufacturers of magneto-resistive sensors include Aichi Steel, Honeywell2, Memsic and Sensitec. I suspect some hard-disk read-head technology may have helped here. The mobile/smart phone area looks like being a huge coming market for the 3-axis units.
One might well ask when will wrist watches move from unreliable 2-axis sensors to reliable 3-axis units. A good question.
(1) See for instance 'Tilt compensation algorithm for 2-axis magnetic compass', Seong Yun Cho & Chan Gook Park, Electronics Letters, Volume 39, Issue 22, 30-Oct-2003, pp 1589 - 1590
(2) See for instance United States Patent US6836971 'System for using a 2-axis magnetic sensor for a 3-axis compass solution' assigned to Honeywell. Note that this patent requires the use of a separate tilt sensor as well as the magnetic field sensor. Watches don't have tilt sensors.
Long Term Report - 1-May-2010
Later Test Conditions & Locations
In late March my wife and I did a 9-day trip around the Australian Alps, from near Mt Jagungal to Mt Kosciusko and Thredbo Village (food drop), and then back again by a different route. Most of this trip was between 1,500 m (4,900') and 2,200 m (7,200'), although at Thredbo we did drop down a little below that. The days were warm enough - mostly, but the nights did get down to about freezing. Winds got up to 100 kph (62 mph) at one stage. I took both the WS4 watch and the 'other' one for comparison. Near the end of April we did an extreme 5 day walk in Wollemi National Park and took both watches there. Apart from that there have been some short day walks around home.
In the top graph here we have the altimeter readings. The red line is the data from the WS4; the blue line is the difference between the WS4 and the 'other' one. What stands out from this graph is that the difference between the two altimeters (blue line) was all over the place. This is rather strange for a silicon sensor which normally has very little hysteresis. However, looking at the red line we see that it looks very flat for several extended periods. Looking closely at the numerical data I found that the altitude reported by the WS4 was really flat - like within 1 metre, for most of the times when the watch was at home sitting on my desk. However, there are curious shifts of up to 80 m associated with trips. For instance, the altitude at my desk was sitting constant at 166 m before we went to the Alps, and it sat constant at 242 m after we returned. After we returned from Wollemi it sat constant at 279 m. I know my house did not move by that much while I was away!
There is one simple explanation for all of this, and it is one I don't really like. I believe that the software in the WS4 watch, like in another watch/altimeter I have, attempts to compensate for slow changes in the weather. This looks fine from a casual marketing perspective, but from the point of view of a user in the field it makes the altitude reported very unreliable. Significant static shifts can and do happen, and they can accumulate too. This plays hell with any attempt to use the altimeter to determine height in the mountains over several days, and consequently I can no longer trust this altimeter. Without a trustable altimeter feature the WS4 is simply a huge (some might say oversized) watch. I did ask the company about this as there is nothing at all on the web site about it, but I did not receive a reply.
The lower graph shows the offset between the two watches and the NIST time. Both trends continued quite stably much as they were earlier - subject to one small point. It is well-known that even good crystal oscillators have a temperature coefficient, and can change frequency by a small amount (parts per million) when there is a large temperature shift. I think this is visible in the results, at the long gap in the readings at the end of March where I was up in the mountains and to a lesser extent at the end of April. Both watches seem to have suffered a shift in their offsets during these trips, but the WS4 has suffered worse. I ascribe the shifts in the times to the cold nights we experienced. In fact, I noticed that one of the watches was struggling one morning when the temperature was about 1 C (33 F): the display was a bit faint and the 'low battery' indicator was showing. Both problems disappeared when I warmed the watch up in my pocket. Well, this is reasonable. Later on I kept the watches in my sleeping bag overnight to 'help' them along.
Customer Service Continued
Around the end of March I was away on a trip in the mountains. On my return I found the promised wrist strap had arrived. That was very pleasing.
The pictures here show the 'replacement straps'. Included in the kit sent were not only the straps but also the massive outer shell, as shown in photo A. It would seem that the easiest way to change the watch over from the long nylon strap to the shorter plastic straps is to move the inner module over, from shell to shell. This is done by undoing the four screws in the back of the shell and removing the back face, as shown in photo B. The screws come out of the holes indicated by the red arrows. Removing and replacing the back face is in principle fairly easy, with one exception.
The exception is the O-ring seal, indicated by the yellow arrow. The O-ring is very thin, and must be properly in the thin channel made for it in the main body. In the photo the O-ring is not in the channel near the yellow arrow. Without this O-ring properly in place water would get inside the watch just from splashes.
Also shown in photos B & C and indicated by the blue arrows is the fairly traditional pin which holds the watch strap to the body. Normally this is removed to replaced the strap. I experimented a bit with this, and found that it is indeed possible to remove the straps from the body by pressing this pin out, as shown in photo C. However, this wasn't easy as the pin is held in by some knurling in the middle of the pin, visible near the middle of the pin in photo C. I had to use a high-tensile 1 mm rod and considerable force. Then I found out what the two pseudo-bolts indicated by green arrows in photos A & C are for. They are actually fancy press-in plastic studs which help hold the strap to the shell. There was also some superglue (I think) between the strap and the watch shell indicated by the purple arrow. I have to say I fail utterly to see why such overkill is needed: even very expensive watches rely on the simple pin.
I tried the plastic wrist strap but found the watch was still too huge for me to be happy wearing it on my wrist.
These are my admittedly biased personal opinions. The WS4 watch works, but it is far too big on my wrist when I am out walking. The time-keeping is fine, despite the small measured drift. The altimeter is spoilt (in my opinion) by the software which tries to track the weather: I cannot trust the readings to much better than 100 m (300') because of this. Quite frankly, an error of 100 m makes the altimeter section almost useless for my needs. I don't use the compass feature because it is so unreliable when tilted even a small amount. Other features were not tested as they were of no value to me.
The subsidiary displays on the watch face (analog time, weather and temperature) are of no benefit to me and just make the watch face bigger. The alarm is too high-pitched and quiet for my (aging) ears, but this is common to most watches. The large number of other ancillary features are of little or no value to me, but they don't actually get in the way. The business about being 'resistant to 50 m' annoys me because it seems so misleading - at least to me, but that is an industry-wide problem.
I think this watch is aimed not at the outdoors walking community but at the young male machismo market. Granted, that's a big market, so I wish the company well there. I just wish someone made a small reliable watch / altimeter without the other unwanted 'features'.