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  • Home made Talyvel

    Came across what appears to be cheap level sensors... specs as follows.. With the discrimination being 0.01 arc seconds would that mean with a suitable driver and reader they could be used as something similar to a talyvel? And thus used as a very sensitive talyvel type machine?


    AS A TILT TRANSDUCER

    Linear Range (typical)

    Linearity Error (max)

    Asymmetry Error (max)

    Unambiguous Range

    Discrimination

    Datum Change
    for ±5 ° Tilt about Cross Axis (max)

    Temperature coefficient
    with Matched Detector
    -10°C to 25°C
    +25°C to + 60°C

    Datum Temperature Drift (max)

    AS AN ACCELEROMETER

    Linear Range

    Unambiguous Range

    Equivalent Pendulum length

    Undamped Natural Frequency

    Damping Factor at 25°C

    PHYSICAL PROPERTIES

    Datum Stability Long Term

    Datum Stability Short Term

    Settling Time to <1%
    Value



    ±0.5

    1.0

    2.0

    ±2.0

    0.01


    1




    0.2
    -0.1

    0.3



    ±0.01

    ±0.1

    305

    1

    0.6



    10

    1

    5
    Units



    Degrees

    %

    %

    Degrees

    arc-seconds


    arc-mins




    %/°C (max)
    %/°C (max)

    arc sec/°C



    g Units

    g Units

    mm

    Hz





    arc-sec/month

    arc sec/hour

    seconds
    Precision takes time.

  • #2
    Good question.

    Here is the web page:

    http://www.taylor-hobson.com/electro...inometers.html

    The report/specs from the web site for the better electronic version is:

    Digital Clinometer

    Digital Inclinometer Is a robustly constructed instrument designed for clear simple reading, the system is ideal where precision angle is required over a large range.

    All four quadrants of the system are precision machined making it possible to measure angle from any side.

    The system has the ability to work from absolute or relative modes through a simple push button operation.


    The battery power, sturdy design and compact construction make it ideal for almost any situation, features include;
    •Built in calibration program ensuring measurement integrity
    •Direct reading to 4 arc secs
    •Accuracy to 2 minutes of arc
    •Large measurement range +/- 45 degrees
    1 minute of arc = 1/3600 degrees

    2 minutes of arc = 2/3600 = 0.000055555 degrees the sine of which is: 0.0000097 the inverse of which is 103,132 which is 1mm per 103,132mm or 0.001mm per 1,031 meters which is very good.

    As surface plate calibration (even USA-made ones) are metric where the units are in metres and um (aka microns = 1 millionth of a meter = 0.00004" (ie 0.4 "tenths" of and inch)).

    That on the face of it is very good indeed.

    I wonder what the cost is?

    I'd like someone to check my maths though - just in case I've got it wrong.

    Comment


    • #3
      I think one minute of arc is 1/60th of a degree. And you added an extra zero in the 0.000555 figure.

      Igor
      Last edited by ikdor; 12-17-2012, 06:43 AM.

      Comment


      • #4
        Came across what appears to be cheap level sensors...
        Found here: http://www.tilt-measurement.com/dshe...es/elh100.html

        How it works: http://www.tilt-measurement.com/appn...les/anim1.html

        Other products: http://www.tilt-measurement.com/sfc.html

        The sensor looks deceptively(?) simple, but the spec (discrimination of 0.01 arc seconds) doesn't sound cheap to me !!

        Cheers

        .
        Last edited by Barrington; 12-17-2012, 07:22 AM.

        Comment


        • #5
          Sure it may have that resolution, but notice that it is not so linear on all the scale length. But same can be said for a dial test indicator: very good at showing runout, but doesn't actually measure how much exactly.
          Amount of experience is in direct proportion to the value of broken equipment.

          Comment


          • #6
            Originally posted by ikdor View Post
            I think one minute of arc is 1/60th of a degree. And you added an extra zero in the 0.000555 figure.

            Igor
            Thanks Igor - it was a silly mistake.

            Comment


            • #7
              The Talyvel resolution of 2 arc seconds is fine and as Barrington says is probably quite (very?) expensive too.

              Compare it with the Starret 199Z Master Precision level (with 10 second accuracy) the features of which are:

              Specially designed to set up, check and test machinery of all types
              At-a-glance reading of the exact variation of machinery levelness
              Auxiliary level vial shows lateral position and assists in horizontal setting
              Level vials are positioned so breakage is reduced to a minimum
              Fool-proof adjustment
              Seasoned, machined castings
              Finished wood case
              Groove has a special involute design, permitting better centering and greater capacity to handle larger rounds
              Groove and bearing flats are machined together for maximum accuracy
              Ground and graduated main vial of 10-second accuracy; one division equals 1/2 thousandth (0.0005) of an inch per foot, or 0.04mm per meter
              Main vials have seven graduations on each side of the bubble
              Special alloy iron used to obtain freedom from thermal effects
              All level bases are made from the finest quality seasoned cast iron and are precision-machined on the reference surface
              Scraped reference surface
              http://www.starrett.com/metrology/pr...ls/Levels/199Z

              Comment


              • #8
                I guess you could say this thread has been tiffified..
                Precision takes time.

                Comment


                • #9
                  OK, I'll bite. Here's my allotted silly question for the day. What the H*ll is a a Talyvel?
                  Keith
                  __________________________
                  Just one project too many--that's what finally got him...

                  Comment


                  • #10
                    http://www.taylor-hobson.com/electro...inometers.html

                    A pretty accurate and probably quite expensive up-market levelling machine and a vertical angle (inclinometer) measuring device.

                    Comment


                    • #11
                      Originally posted by oldtiffie View Post
                      http://www.taylor-hobson.com/electro...inometers.html

                      A pretty accurate and probably quite expensive up-market levelling machine and a vertical angle (inclinometer) measuring device.
                      Thanks. I are now officially enlightened...
                      Keith
                      __________________________
                      Just one project too many--that's what finally got him...

                      Comment


                      • #12
                        The sensor looks quite simple. It's be nice to know if the price matched the simplicity.

                        I was toying with the idea of making a Talyvel clone using a pendulum and differential capactors coupled to a Blumlein bridge and a lock-in amplifier (rather than the inductive proximity probe that T&H used). In fact a Bentley Nevada proximity probe and a 2" pendulum will give 2mV/Second of arc for a reasonable price.

                        This all became superfluous when I eventually picked up a Taylor & Hobson 0.2sec autocollimator. Still got to make the mirror mounts to use with that though...
                        Location- Rugby, Warwickshire. UK

                        Comment


                        • #13
                          That's quite a machine:

                          http://en.wikipedia.org/wiki/Autocollimator

                          http://www.google.com.au/search?q=g&...w=1920&bih=846

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