Taylor-Hobson Talyvel 4
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  1. #1
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    Default Taylor-Hobson Talyvel 4

    I've just purchased a old Taylor-Hobson Talyvel 4. The seller described this as "ancient, but in good working order".

    For those who are not familiar, this is a precision differential electronic level with two read heads (A and B). It has an LCD digital display with a resolution of 0.1 arcsec and a range of +-600 seconds, and a claimed accuracy of 0.2 arcsec near zero. It can display A, B or A-B, which is nice because by parking head B at a fixed position and moving only head A, you can compensate for any shift or tilt in the machine.

    The level won't be delivered for another week, but meanwhile I am gathering information. Taylor-Hobson sent me an instruction manual by email, which includes the procedure for balancing the bridge circuits in each head and for setting the gain correctly.

    Does anyone here own a Talyvel 4? I'll post some photos and a report after I have received it.

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    Hi Richard,

    Thanks for the links. The latest model (Talyvel 6) appears to use exactly the same read heads as the model I am getting (Talyvel 4) but modern electronics has been grafted to the top of the read head to eliminate the big central control box. The fundamental accuracy of 0.2 arcsec has not changed.

    If anyone here owns a Talyvel, I would be happy to hear from them.

    Cheers,
    Bruce

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    Hi,

    I have a Talyvel 4.

    When I purchased it, it only had one sensor.

    I used it when I lapped my granite surface plate. I had to
    always stand in the same exact spot so any disturbance tilt
    would be the same for all readings.

    I talked with the manufacturer to see if they had another sensor,
    and they did not. They said I could use one generation older sensor.
    So I purchased an older unit, but I have yet to calibrate both of the
    sensors.

    When you get your unit you will need to make sure that the 'A' and 'B'
    sensors are labeled and calibrated to the respective amplifier connector
    before you use it.

    Paul

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    Hi Paul,

    Thanks for responding. Glad I'm not alone.

    Quote Originally Posted by toolnuts View Post
    When you get your unit you will need to make sure that the 'A' and 'B'
    sensors are labeled and calibrated to the respective amplifier connector before you use it.
    I read the procedure in the manual (first setting the balance, then setting the gain) and it seems straightforward. I'll do this first thing as a way of checking that the Talyvel works as it should.

    Cheers,
    Bruce

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    I have a Talyvel 2.

    When you consider the price they sell for, if you got the Talyvel 4 in working condition for less then a few thousand euro, you got a bargain.

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    Good Day, Bruce --

    I can't recall ever working with a Talyvel electronic level, but if you should find yourself plotting a contour based on "stepped tilt" measurements such as used in the Moody Method, it's important to know which direction the instrument -- be it an electronic level head or an autocollimation mirror -- was moved. Plotting A-to-B measurements as B-to-A measurements will make a concave surface appear convex, and vice-versa.

    An obvious indicator of such a fault is a plot showing a convex profile in one direction that doesn't intersect a concave profile in a roughly-perpendicular direction, but I've encounterd a couple cases of every profile plotted in the wrong direction -- which produces a self-coherent plot that shows highs as lows and lows as highs.

    John

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    Hi Paul,

    Quote Originally Posted by toolnuts View Post
    I have a Talyvel 4.
    I have another question. According to the manual, the main Talyvel 4 display unit contains a set of NiCad batteries. Do you know if these are needed if the unit is connected to mains power? Or are they to allow operation remotely where mains power is not available?

    The one that I bought must be about two decades old. Unless the batteries were replaced more recently, they are probably in poor shape. Do you know what types of NiCads are used? Are they standard cells that can easily be replaced?

    Cheers,
    Bruce

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    Hi John,

    Quote Originally Posted by John Garner View Post
    If you should find yourself plotting a contour based on "stepped tilt" measurements such as used in the Moody Method, it's important to know which direction the instrument -- be it an electronic level head or an autocollimation mirror -- was moved.
    Yes, that's right.

    Some time ago I calibrated my surface plate (800 x 1200mm) with an autocollimator using Moody's method. I was surprised to see that Moody's paper never specifies how to determine the overall sign, though it's not hard to figure out. In addition to this omission, the paper also contains a half-dozen typos/mistakes. Most of these I found after writing my own computer program to compute the 8 worksheets and to draw plots of the surface. I checked my program by entering Mood's example data and comparing the resulting worksheets.

    The result of this was that my surface plate is low in the middle by about 10 microns. A plot is attached (unfortunately the PM system reduces the resolution so you can't read the axes scales, but the vertical axis goes from 0 to 10 microns). One of the reasons for getting the Talyvel 4 is that I would like to try to improve the geometry by lapping, but to do this will need to keep checking the geometry as I proceed. I found the autocollimator approach very tedious and fussy and hope that the levels will be easier and faster.


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    That´s a very nice plot Ballen, I´m seriously impressed by your skills.

    I got an autokollimator recently although I have not used it much yet. Got some advise over in the metrology forum as well. I wanted to do the same thing but ended up making do for now struggling with vermont photonics demo program. A bit cumbersome and no way to save or print the results but can take a screenshot just for reference sake for home use.

    That Talyvel is for sure a nice thing, congratulations and I hope it will serve you well!

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    Thanks. If you can compile and run a C program you are welcome to use my code. I've sent you a link to it offline.

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    I've also got an autocollimator, a stock of λ/20 mirrors that I got aluminised and a couple of cast iron surface plates to re-scrape and use as laps on my surface table. But I have not used it yet.

    I need to calibrate and/or re-lap the surface table because I am not certain that it is accurate enough for when I rebuild the surface grinder.

    If you could share your source code in this direction, you would save me a week of work!

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    Quote Originally Posted by Mark Rand View Post
    IIf you could share your source code in this direction, you would save me a week of work!
    Sure, happy to share. Github, search for "moody surface plate".
    Last edited by ballen; 07-27-2019 at 12:38 PM.

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    Hi Bruce,

    I haven't had to worry about the batteries yet as
    they still hold a charge.

    Paul

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    Quote Originally Posted by toolnuts View Post
    I haven't had to worry about the batteries yet as they still hold a charge.
    When the batteries are charged can you run without mains power? I have not understood if the batteries are always needed, or just when running off the grid.

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    Thank you Ballen, that is most kind of you!
    I hope i can return the favor one day in some way.
    Im not a hacker in any way but i can find local help to get it running for sure.

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    Ballen,

    On the question, does it require the batteries.

    This is a very sensitive instrument, and if you tried
    to run it without the batteries you most likely would
    see the ripple current from the AC.

    Paul

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    Hi Paul,

    Quote Originally Posted by toolnuts View Post
    This is a very sensitive instrument, and if you tried to run it without the batteries you most likely would see the ripple current from the AC.
    I find that hard to understand. The bridge circuit used to sense pendulum position operates in the audio band at a few kHz. When the Talyvel4 was designed and being produced (mid 70s) there were plenty of inexpensive and simple "ripple eating" circuits that could virtually eliminate power supply noise at a few kHz. The stray noise that remains is probably dominated by pickup of environmental magnetic noise from power wiring and motors outside the unit, which would also be present under battery operation.

    [EDIT]

    I looked again in the Talyvel 4 manual, which says:
    "The Display Unit is powered either directly from the mains, by rechargeable batteries or in an emergency, two dry batteries of the PP9 type can be fitted."
    This leads me to believe that the batteries are there for off-net operation only.

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    Thank you very much for the link to your code. My C was good 25 years ago, but I only did graphics in HP Basic and not on any unix or windows machines, so that is a great help to me.

    It has been a few years since I have owned anything that used PP9 batteries.

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    The Talyvel4 arrived yesterday and I've started checking it out. Starting to add some information here that might be useful for others in the future.

    BATTERIES

    There are two Ni-Cd batteries of type RS 229-059, 8.4V Ni-Cd, 1.3Ah, PP9 size
    RS PRO 1.3Ah NiCd 9V Rechargeable Battery | RS Components

    The unit can run either on mains or on battery power.

    To run on mains, there is a mains switch in the back. When that is turned on, then the unit charges the Ni-Cd batteries if needed, and also operates the level functions from the mains.

    There is also a power switch in the front, via a 4-position rotary selector with OFF, A, B, or B-A. If the mains switch in back is OFF and the rotary switch in the front is on A, B, or B-A, then the unit runs on battery power.

    On my unit the batteries have a sticker showing that they were replaced in 2014. Hopefully they still have some life left, but this will depend upon their past usage, since Ni-Cd batteries suffer badly from memory effects.


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