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  • Evan
    replied
    If he is a she how do you manage to get the last word in ?
    We don't.

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  • John Stevenson
    replied
    Originally posted by Evan
    First of all, she is a she. And, she knows a lot more than 50 words. Furthermore, she isn't allowed to answer the phone.
    If he is a she how do you manage to get the last word in ?

    .

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  • oldtiffie
    replied
    Start a new thread and leave this one to the "Lawyers"

    Deleted/erased-out
    Last edited by oldtiffie; 08-20-2007, 07:36 AM.

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  • Evan
    replied
    Strangely, you seemed willing earlier to agree the Albion temperature compensation was a joke.
    Huh? You must have misinterpreted what I wrote.

    it does nothing more than add or subtract the effect of any temperature differential between the part and the gage.
    Not according to their description. It also relies on an accurate characterization of the temperature response profile of the instrument and compensates the instrument itself, independently of what is being measured. I'm not playing word games.

    It does not compensate any more than someone with a couple of temperature probes and a $2.00 calculator is capable of doing.
    That would be called "manual temperature compensation". It requires a good profile of the instrument response at different temperatures. The only real difference between manual compensation and the Albion products is automation.
    Last edited by Evan; 06-09-2007, 11:33 PM.

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  • JCHannum
    replied
    Strangely, you seemed willing earlier to agree the Albion temperature compensation was a joke. Whatever their salespeople choose to call it, it does nothing more than add or subtract the effect of any temperature differential between the part and the gage. It does not compensate any more than someone with a couple of temperature probes and a $2.00 calculator is capable of doing.

    You can continue to play word games if you choose.

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  • Evan
    replied
    The Albion products have been previously dicussed, and do not offer temperature compensation, but temperature correction via a computer.
    The computer cannot be separated from the instrument in many cases. What is the difference between compensating mechanically or digitally? What then would be a temperature compensated digital caliper compensated by it's internal computer?

    Funny, Albion thinks they offer temperature compensated instruments. They say so on the web page. It says "Temperature Compensated Dimensional Gaging".

    As for invar, using a low CLE material is a way to compensate for the effects of temperature. Invar is used in the framework of the Hubble Space Telescope as part of the temperature compensation system.

    As for the insulation on a micrometer, it is there to compensate for the effects of handling, as in "counterbalance" by preventing heating of the instrument.
    A compensating mechanism need not be active, it may be passive and an inherent feature of the design as in my telescope. In the design of my milling machine I have compensated for the possible effects of differential expansion of the steel vs the aluminum by static features of the design such as balancing of forces and allowing movement in ways that do not affect the accuracy or deform the frame. The mill is temperature compensated simply because of the way the parts are put together.

    As I said earlier, many items are temperature compensated by virtue of their design or selection of materials or both.

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  • John Stevenson
    replied
    Who in their workshop can work to anywhere near these limits being discussed ?

    Unless you have a close fitting door the draught's can knock the average South Bend off by 2 thou.

    Most of the gear we are using was made by people on piece work with families to feed.
    Not perfectionists with time to spare and no though of cost.

    True there were some pieces of equipment that were the exception to the rule but you need open wallet surgery to afford these.

    .

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  • JCHannum
    replied
    I was referring to metrology labs, not chemistry or physics. That kind of goes with the subject being discussed. I should have said metrology or inspection labs. (Slaps hand.)

    The Albion products have been previously dicussed, and do not offer temperature compensation, but temperature correction via a computer. Apparently you forgot that distinction had been pointed out.

    Invar tape is not temperature compensated, it merely has a very low coefficient of expansion, making it change less over a given temperature range. It still is correct only at standard temperature. Other, more commonly used materials for surveyor's tapes include steel, cloth and fiberglass.

    Insulation is common on micrometers, and other measuring instruments, as is the practice of handling with cotton gloves or chamois as previously mentioned. That is to reduce the effect of heat fron the technician's hand. It is not temperature compensation and, in fact, is used because the instrument is not temperature compensated.

    I raised the question about time since you offered a watch as an example of a temperature compensated instrument.

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  • Evan
    replied
    Jim said:

    If the need for temperature compensated measuring instruments were a MUST, they would be readily available. I have yet to turn up one in any form.

    I do see a few CMMs that claim temperature compensation, but further reading reveals most are apparently temperature adjusting ala the Albion gage. They compare temperatures at various points, and use a computer program to bias the output. This is not true compensation as being discussed here.

    Of all the catalogs I have, and instrumentation I have had or seen, I have never seen any common measuring instrument, or for that matter, lab or other high precision instrument that has temperature compensation. Many are marked with a temperature, 68*F on older, non ISO gages, to indicate the temperature at which they are calibrated. This information is all that is necessary for the user to make any adjustments needed.
    And then he said:
    But since the topic is dimensional measuring, let's stick to that, not wristwatches and refractomerers.
    You broadened the subject to include "lab or other high precision instrument", not me. There are many that are temperature compensated and often that compensation isn't mentioned as it is standard practice without which the instrument would be useless.

    However, if you wish to stay back on the topic of dimensional measuring then here is an example of a wide variety of temperature compensated shop measuring instruments.



    The link, previously given, is here:

    http://www.albiondevices.com/

    Another example is the invar survey tape, which I mentioned previously.

    Invar Tapes Nickel-steel alloy tapes, known as Invar, Nilvar, or Lovar, have a coefficient of thermal expansion of about one-tenth to one-thirtieth (as low as 0.0000002 per 10F) that of steel. These tapes are used primarily in high-precision taping. These tapes must be handled in exactly the same manner as other precise surveying instruments. The alloy metal is relatively soft and can be easily broken or kinked if mishandled. Ordinarily, Invar tapes should not be used when a steel tape can give the desired accuracy under the same operating conditions. Invar tapes are used for very precise measurements, such as those for base lines and in city work.
    http://www.tpub.com/content/engineer.../14069_391.htm

    Also, why do you think micrometers have insulated grips?


    And how, exactly, does temperature effect time?
    Changing the subject? I didn't comment on that or bring it up.

    I don't know if temperature affects time. It may in theory but I suspect only at absolute zero, which is unattainable. It most certainly affects the instruments that mark intervals, like a watch.
    Last edited by Evan; 06-09-2007, 04:16 PM.

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  • JCHannum
    replied
    Originally posted by Evan
    The common mechanical wrist watch in the better quality versions were temperature compensated.

    You aren't showing much imagination Jim. As the list is much too long to post here try this search:

    http://www.google.ca/search?hl=en&sa...G=Search&meta=
    Er, yes technically. But since the topic is dimensional measuring, let's stick to that, not wristwatches and refractomerers.

    And how, exactly, does temperature effect time?

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  • dp
    replied
    I used to have a Crescent type wrench that would bind up when it got cold. I was working on a radar antenna on an oil tanker in Valdez, AK in a blizzard and had to keep putting it in my pocket as it would become useless after a few minutes. After fighting with it for an hour I tossed it into the harbor. I suspect it had some brass and steel in a conflicted configuration that would lock the adjuster (when it was most needed!).

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  • tdmidget
    replied
    Ahh yes 1,200,000 hits for "temperature compensated instruments" Ph meters and other chemical and process items it appears. Now try "temperature compensated caliper"

    Leave a comment:


  • TGTool
    replied
    Originally posted by Swarf&Sparks
    When I first started programming, I used to dream in Turbo Pascal!
    And don't you just hate it when you've failed to provide for loop termination, and you're just going round and round in the dream, trying to find the CTRL C keys in your head!!

    Leave a comment:


  • Swarf&Sparks
    replied
    "It's commonly accepted that you cannot read anything when dreaming"

    When I first started programming, I used to dream in Turbo Pascal!

    Leave a comment:


  • John Stevenson
    replied
    Originally posted by Evan
    It's commonly accepted that you cannot read anything when dreaming, .
    Shush !!

    Were you on our side in the last war ??


    .
    Last edited by John Stevenson; 06-09-2007, 02:28 PM.

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