How Accurate Are Low Cost Digital Calliper Micrometers?

The Angular measurement:- MILS is of japanese origin and as stated is 6400Mils to a 360 Deg. circle. Any errors are very small and ignored.

Then at 1000 Mtrs 1 MIL will subtend 1 Mtr and so on, at 2000 Mtrs it will subtend 2 Mtrs.

10000mtrs it will subtend 10Mtrs.

Then graticules are marked in Mils and it is very easy in the Horizontal plane to see how far off a fall of shot is and use that to make angular corrections.

It makes a very good range estimate for the ranging of fall of shot on artillery and is now standard in the British army.

Hand Compasses are also marked in Mils.

Clive

I have a couple of digital calipers, the expensive one drains the batteries, the cheap one doesn't, go figure.

I've found that my biggest problem is that there's enough flex in the instrument to give a constantly fluctuating reading in the half a thou. or less isle. I end up physically holding the jaws together with one hand to get a steady reading, while tightening the lock screw with the other.

My favourites are my three dial calipers, one imperial, one metric and one fraction, which was given to me by a universal joint rep forty years ago.

Ian

much appreciated

Clive,

The story of the mil is more complex than you suggest - and, BTW, I can find no trace of it having any Japanese origin.

In order to have the same relation that you set out - i.e. 1 m separation at 1000 m - the angle would have to be 1/1000 radian, or 1/6283 of a circle. This was adopted by the infantry for sighting rifles. Then for some reason the artillery decided they wanted to simplify it to 1/6400 of a circle, so that 5 binary divisions gave 100 mils (probably - though this is only my guess - because this made it easier to construct by geometry). Just to add to the confusion the US artillery had previously used the mil to represent 1/1000 of a right angle (i.e. 1/4000 of a circle).

It seems to me that the only one of these which has the merit of actually being useful is the infantry mil of 1/1000 radian. However, I have only ever come across the mil as a military unit.

Source - mainly the Oxford Dictionary of Weights and Measures.

David

Edited By David Littlewood on 08/05/2012 15:34:53

WILD Heerbrugg and now LEICA have always been able to supply theodolites in MILS and GRADS/400.

I have converted many standard 360Deg, instruments for various establishments. Particularly the T2 Theodolite. which is accurate to half a sec. with Auto Collimation. and similarly in the other configurations.

These being mainly used by Military and Shipbuilding. Also used to align aircraft navigation devices and weaponry, ie High Intensity Lights. and in submarines to align torpedo tubes and optical systems. They can be supplied with what is called 'Tight' standing axis so that with a fixed compensator can be used in a right angle mode to transfer lines of sight throughout a vessel.

This mode is when the instrument is fixed to a vertical surface.

Gyro based theodolites such as the ARK1 are usually in deg. and are placed in a special jig prealigned to an airframe and then the aircraft is turned and compass checks carried out.

Maybe now not needed due to Sat. Nav instrumentation.

Regards the Japanese origin I can only go by what I was taught as an apprentice and had no need to research it, only that it existed and how to use it.

Clive

Peter, your reference to "mils" above as a measurement of 0.001" is quite correct.  Also was  Strowger not an American?

Edited By Morgan Sweet on 12/05/2012 20:48:21

Edited By Katy Purvis on 01/06/2015 12:27:04

Morgan,

Yes, the Strowger System was reputedly invented by Almon B. Strowger who was indeed American, but the system was much refined into the eventual workable system that we all love. Or hate!

Having said that, the GPO as it was, initially used Strowger type selectors from a number, five I think, of different companies, which although they fitted a standard cradle and bank, were between themselves not really compatible, ie spares for Siemens, say, would not fit, say, ATE. Then, in the '30's I think it was, the GPO designed it's own Strowger selector which was called the 2000 type and all manufacturers built to this design, hence solving the spares compatibility problem.

The 2000 type selector had a number of other advantages as well over the older selectors which became known generically as pre-2000. The 2000 type switch lasted until the demise of the Strowger system in the UK although there was an attempt in the '60's to introduce a cheaper alternative. This was, unsurprisingly, known as the 4000 type selector and was functionally identical to, and hence fully interchangeable with, the 2000 type and used the same cradle and bank. However, it did not last because, I believe, it was not as reliable as the 2000 type.

Peter G. Shaw

Edited By Peter G. Shaw on 15/05/2012 17:32:02

I did manage to get my paws on a 25mm and a 50mm standard ( both labeled +- 0 μ ) yesterday and - sure enough - it turns out that in ideal conditions my cheap digital calipers do give a better than advertised accuracy

(PS - I remember using military compasses marked out in Mils - a special drill if you broke one of them - the glowing paint was radioactive. Microchips can never match the magic of the Strowger exchange.)

Edited By Will Robertson on 09/06/2012 21:22:00

Presumably it has been decimated...?

Regards,

Tony

...and those Metric bigots all seem to be just a bit too "holier than thou" don't they?

I'll get my coat...

Regards,

Tony

Reduced by 10% That would leave us with ninometers.

What I can't understand is why we use hectares instead of ares.

I'm off for a hectolitre of best scotch.

Neil

It all goes to show that units of measure are a pain in the ares. Mind you, after a hectoliter of best scotch, you would have a wee pain in the wallet, not to mention the head

Regards,

Tony

Hmmmmm, I can't work out if I'm being agreed with, or insulted............

Andrew

PS: I am assuming that people understood the mathematical connotations in my original post.

Those were the days! I have worked on all thiose systems, before moving onto Crossbar, TXE2 and 4 and finally system x and y.

While the older strowger type equipment kept a lot of TO's inemployment with an amazing array of adjustment tools. the modern electronic sytems we now have, only require the TO(i think there must only be one left now!!!) to have an Alsation dog rather than a toolkit.

The dog being there to stop the TO from touching the equipment, as engineers messing with the kit caused more problems than leaving it alone.....................

Well, they were clearly either real or imaginary...

Regards,

Tony

PS: I am assuming that people understood the "thou" pun too.

Howard,

A question.

Are you the Howard Winwood from Sheffield who used (I think) to work with Steve Bass whose line manager was John Seymour during the early '90's? Because if so, I was on the same group at that time. And no, I'm not the EL&P Peter Shaw.

If you are, you may wish to converse via private messaging.

Regards,

Peter G. Shaw

Edited By Peter G. Shaw on 14/06/2012 15:31:54

Tony,

We need to root this out. It's avery bad sin, cos everythings going of at a tangent. Its a prime candidate for some sort of reciprocal arrangement, before everyone is divided into warring fractions.

Neil

Neil -

Too much more of this hyper-bolics & we will all be under the cosh.

Regards,

Tony

You lot are all vulgar factions!

I no , i no, it's speld rong!