So, today I found out something interesting. Roche has two slightly different versions of the XS PT strips, this apparently is related to the INRange series of devices. I went to order some more strips from my (online) provider (here in Australia) and found the following two products (at different prices). There is the XS PT Test (which I've used for well over 10 years).
And the new kid called the XS PT Test PST (probably with KyB4 and other enhancements)
I'm seeing that this one has INRange written on it as well as XS written on it. Further to the best of my knowledge the INRange is the same and compatible with the XS and as a unit simply has some additional features more conducive to working in a Clinical setting, such as the ability to interface with a computer, multiple ID tags (presumably to differentiate different patients) a nice colour screen (whoopdie do) and a graph (I prefer what I do in Excel).
So I rang Roche (in Australia) and spoke with a "Technical Support" officer who informed me that the two were interchangeable but there may be some differences in electronic communications. She was surprised when I said that my seller has a different price on the XS PT Test vs the XS PT Test PST.
She also said to me that she thought that the difference between the names was PST was for "Patient Self Testing" ... (making me wonder what's happening over there in the Good Ole US of A)
All very interesting. Given that I have the XS (and not the INRange) I'll be using the earlier (and cheaper) ones in my XS ...
This is the new (looking golden) and the old (poor camera colour balance on my part)
Everything (including the amount of stripes of contact points) seem to be the same.
I don't know why its taken me so long, but I finally figured it out.... all it took was this WW1 trench watch homage and a new leather strap to work it out.
Readers of my blog will know that I've long derided NATO straps as being (for civilian use) a problem looking to be a solution for. I've likened the whole stupidity of an extra flap under the watch as being akin to wearing tie your self bow tie tied badly, when you're supposed to be at formal black tie evening.
Bringing nothing but bulk behind your watch, puffing it out further from your wrist for no actual benefit (kiddiez who can't actually think will squeal and say "sir sir ... its to prevent watch loss if you break a spring bar", yet any single pass strap will do that) I really don't get why NATO straps are considered "premium".
But as Carl Jung so succinctly put it:
I'm not as polite as Carl so I'll say "... that's why most people are stupid." Which is why this NATO thing persists. People often have no experience, see it as being military or "James Bond" and don't think further than that.
But, wait, today I've discovered the KingWang solution which I will present to you here (and we all know, King Wang likes to watch).
Firstly if you don't have a 9" wrist the leather NATO just isn't going to work because, not only is there the extra thickness, the bloody buckle that anchors the useless flap gets in the way of allowing the watch to curve around your wrist.
As shown above. This is especially a problem with larger watches on a (does this big watch make my skinny wrist look too much like a chicken leg?) small wrist; such as my 6.5" wrist.
Once one thinks like the Ministry of Defence (using military intelligence) we can see the obvious. This cunning lacing style is an optimal solution because it not only protects the watch crystal from being scratched or broken as well as fitting perfectly, but solves the issue of bulk by only having one layer of leather under the watch.
So I present to you the ultimate optimal lacing technique for threading your NATO strap, having it fit and protecting your watch for those too challenged to use a pair of scissors and cut that flap off.
All jokes aside, this is the watch on my Green (started as a) NATO and the Red strap (now having had its useless bit cut off) beside it.
The Green one is a very comfortable waxed leather. Each strap was under AU$25. 22mm thickness which of course is not proper NATO either.
The commonly called NATO strap has several written characteristics, and probably many more unwritten characteristics.
The current military specification strap comes in only one colour (Admiralty Grey) and one width (20mm). The hardware specification is chrome plated brass with a recessed buckle to receive the tongue. Length 280mm, width 20mm, thickness 1.2mm.
It is currently defined in Ministry of Defence, Defence Standard 66-47 as Strap,Wrist Watch.
The Roche CoaguChek is pretty much the backbone of my personal self management of my INR. I have on many occasions discussed that I compare it to the lab and often get quite good (less than 0.2INR units) correlation with labs. This is something which is occasionally still debated (particularly on the internet) but which to my mind was put to bed back in 2012 with many comparisons of its accuracy vs that of other systems. So I'll not waste your time and repeat that here.
Determining INR is based on measuring the time taken for "coagulation" to occur.
Note: That's a minefield right there, so lets just leave it simply at: a timer is started and stopped when the machine determines coagulation is "completed" (*according to guidelines like reagent ISI, another rabbit hole for you the curious).
The CoaguChek uses "amperometric electrochemical" methods for determining the time to declare the point of "coagulation" to stop the timer. A good summary of this and other methods is here (link).
So having swept that detail off the table, I wanted to get down to exploring a little bit about the CoaguChek XS system which we can easily see, but may not have noticed (even if you've used one).
First, lets have a quick look at the strips, they are much bigger than the strips used by Blood Glucose monitoring strips. Shown below.
Obviously the strips above are used because I prefer not to risk contaminating them for photography and so you'll see traces of my blood in these images. Note that circular hole in the strip at about the 24mm point. I'll circle back to that.
This video gives a quick walkthrough of the XS.
As you saw in that video the CoaguChek strips have three layers of plastic, seen in the image below.
The top printed layer is white, in the middle is a black layer which is used to form the blood capillary tube and then there is a clear base layer (which I'll call the substrate). I can't measure the thickness of the black layer, but I used my trusty digital callipers to measure what I could and thus determine the thickness of black layer. The thicknesses of the strip will tell us about the thickness of the blood channel
white part is 0.36mm
the clear base is 0.35mm
the entire width of the strip 0.89mm
and so thickness of the black strip is 0.18 mm (which is the depth of the blood channel). I could have tried to get a feeler gauge in that overhang, but did it this way instead.
Now we know that Amperometric analysis is used and (from this obscure source) know that the XS system uses a lyophilized reagent (reagent in dried form). The reactive components of this reagent consist of thromboplastin and a peptide substrate. In that above link (here again) chapter 5.3 is of relevance to the CoaguChek XS. But basically the blood needs to flow past the thromboplastin reagent and starting the process. You can see where it goes in and where it ends up in this picture of the underside.
Note that the hole allows the capillary attraction to pull the blood through (from where you placed the blood) across the chemistry, through to the area where the sensing occurs. You can see this below too.
The hole is needed to allow the blood to flow right through this channel, and I assume that a light shone through the hole indicates that sufficient blood has now reached the end of the channel.
You can see clearly below that it is a hole below
So from all of this we see how the blood flows, why you need to put the blood on the top of the strip, or if you use the side (also mentioned in the documentation). From the Roche CoaguChek XS manual:
Exploring the 15 Second rule and outcomes
So, for those who are interested
however, as always I encourage people to not only adhere to that 15 second rule (and myself follow it) but to try as much as possible to treat it as a task that you do with accuracy and reproducibility. Do everything the same just like (say) you were making pottery mugs for sale.
Summary
Basically after watching those videos and reading the above you should know more about:
how to use your CoaguChek XS device effectively
be in a better situation to understand why they make a lot of points again and again in the manual like 15 second rule and application of blood, and preparing your finger for getting a good blood sample
You should also be able to dismiss any misinformation you may read on the internet (such as how the blood could coagulate clumps could and block the flow)
from a logical perspective of how the whole system works both physically (the capillary attraction) and the way the machine knows sufficient blood is present.
Knowledge is power and freedom from the anxiety which stems from ignorance.
I'd eye'd this off for a while and finally decided that I would spring for the Mark iii version. I'm attracted to it because
I've always loved the look of the classic Speedmaster
I'm quite a fan of Seiko movements (and this has a VK63 mechaquartz movement)
So its like a fusion of two great houses
I'm not fond of the supplied straps so I put it onto a grey (ex) NATO I had hanging around.
Its smart, well made and frankly I was pretty impressed with the fit and finish. Much ado is made about not having AR coatings (which scratch) but in the days wearing I've found it no harder to read than every other watch I've had in the last 40 years. NOTE: I've since found that it does have AR coating on the inside surface of the crystal (see this post).
As there are plenty of YouTube videos about it I'll only add here some things which are often neglected, such as for instance that it has two holes for spring-bars which allows a NATO to sit more nicely.
Which I thought was a nice touch.
When compared to my SRPE65k1 Seiko 5 its actually not much bigger
I created an overlay of these two in photoshop and while they do not match up perfectly I did center them on the axis of the hands (the issues pertain to my failure to perfectly align for rotation as well as the lens distortions and perspective distortions of phone cameras and their wide angle lenses).
So this has helped me adjust to the Seiko always feeling bigger than I'd like soon after wearing the Pagani ;-)
Also we can see that the PD is not much thicker than the Seiko and would indeed be the same thickness if it had a flat crystal (something I'm entertaining. not least because of the way a convex crystal really exacerbates the reflections, but may not be worth the effort).
Its also worth noting that the springbar is lower on the PD helping it sit nicely on the wrist too. It is however not as comfortable as the Seiko. The Pagani however, worn for a whole day of activity, is tiring and has actually hurt the back of my hand when doing serious labour. This is due to the way the Pagani (and probably Omega) watch isn't sculptured to fit a wrist. Some quick and dirty images to compare these two again.
and the backs:
So the "footprint" is significantly smaller at the back of the Seiko. This is most important when you are actually doing things and your hand is not straight with your arm (like picking things up, supporting your weight, using a screwdriver or a spanner ...) as it is in a brochure picture of a well dressed Gentlman with big wrists. To me this means that the Omega isn't a daily wear watch for anyone except an office worker.
Interestingly on the Apollo missions they wore these watches on the outside of their jump suits, not against their skin. So the PD has become the watch I wear for smart casual or when driving the car for a longer journey. Here it often sits better in a place of visibility and I do like timing things (like a section of a route). Measuring elapsed time is what this watch is really all about.
Interestingly at 65.8g its not much heavier than the Seiko (6g heavier).
I found it very legible (reflections not withstanding) and didn't feel "bigger on the wrist" than my Seiko.
So the basics are:
Seiko Mechaquartz (with around 20 seconds a month accuracy)
Sapphire crystal (meh, I'd be ok with acrylic)
apparently very good build quality
and given that it cost me less than US$75 I find that outstanding value for money. Heck the Seiko VK63 movement alone is nearly half that (unless buying wholesale).
Some points which have emerged after a day or so that I've not seen in any reviews:
finishing of the machined surface edges is not really excellent, leaving them looking good, but feeling sharp. The same goes with the crown at the end of it where it touches you. I took some silicon carbide paper and very carefully (with a small strip of it to control it) took the edge off around the base of the watch and on the lugs too.
despite being large, the flatness of the back really helps it sit nicely in place with my small 6.5" wrist.
the positioning of the straps in different holes (as pictured above) makes a substantial difference
Hands, even on the subdials are nicely aligned
I believe I now have a new daily driver. I might even sell a few watches (probably for more each than this cost) to "fund it". I'll be keeping the SRPE65k1 though, its already got too many marks on it for most watch buyers.
Lastly a point on the philosophy
People react strongly about watches which are copies (to be blunt) or homages (to be pretending its something else). Setting aside the fully hand made watch by a craftsman in his workshop, pretty much all modern watches are "reproductions". When seen from the view that; they are designed in CAD, then a machine produces the parts from a file (and in some cases does a lot of the assembly too). From this perspective a maker (say) Rolex just reproduces watches from a design.
I'm looking at my PD-1701 and seeing that others have (by measurement) done a reproduction of this but at a price which can be purchased by anyone who loves the look and design. The real thing that differentiates it is the logo and copyright.
While the PD-1701 is not finished to the microscopic examination of the case and the mechaquartz movement is not a hand made highly complex mechanical one. Most owners of the Omega would probably not know that you had swapped out their mechanical movement until they went to wind it, for they don't actually see the movement in daily life with the watch. Few if any owners would have taken the case back off in the 1960's to see.
Thus these Homages or reproductions are really just enriching our lives (those of us who aren't uber wealthy or willing to make sacrifices to get the originals) with being able to enjoy the essential parts of the watch - how it looks and how it functions - at a much more affordable price. I suspect this desire to be 'exclusive' (meaning exclude you from my club) is what's really hurt in people when they find out "its a copy"
Pagani ... Pagan ... mmmm I think I'm going to proceed with this Mod ...
The watch is not without fault, but for under US$80 its a lot of watch.
Lastly another strap
Lastly while I was happy with this strap I genuinely don't find it worth the extra money of the eBay leather ones which have exactly the same hardware and equal in leather quality. Still it was only 20% dearer.
