Hilger & Watts Autocollimator and Clinometer
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  1. #1
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    Default Hilger & Watts Autocollimator and Clinometer

    Hello,

    Some weeks ago I managed to acquire a very nice Hilger & Watts TA53 Autocollimator and a Hilger & Watts "Large precision clinometer TB80".
    The autocollimator is of the Photo-Electric type, this means that there is a LDR (Light-dependent resistor) built in the autocollimator that can take the readings for you. It does however need a display unit which I am missing, and of course these things are as rare as unobtainium hens teeth.
    So my plan is to build one, perhaps a more modern and sophisticated one with more features.
    My plan is to somehow digitize the analogue signal and send it to an arduino and perhaps a computer.
    My electronics knowledge is somewhat limited so i'm going to need some help, ive already been talking to Peter Lambrecht who made the electrical schematic for the original display unit and got a ton of other information. Thanks Peter, and by extension Daryl Bane!!

    What i'm currently trying to figure out is what voltages go to the vibrator sled and photo conductive cell.
    There seems to be a difference in voltage output to the autocollimator from different types of display units, there is also a difference in resistance in the vibrator sled and photo conductive cell depending on what type H&W autocollimator you have?
    The resistance of the vibrator sled and photo conductive cell on my AC happens to be 44.5ohm and more than 40Mohm (could mearuse properly because my multimeter peaks at 40Mohm)
    In the next post i've uploaded the schematic and a list op component values in the hopes that some of you could help me.

    With my H&W set also came a transformer for the light source but it is very heavy and bulky so i decided to design and 3D print a light fixture that houses 2 AA bateries a switch and and an On/off indicator light. It screws on the back of the original light bulb housing and should work for 5,5 hours with the original buls depending on what type AA batteries you use. Ive included some pictures of the thing.
    If any of you are interested I will gladly share the designes, just send me a message!


    The H&W "Large Precision clinometer TB80" remains a bit of a mystery to me because i cant find anything online, no manual no other pictures of this particular unit. I think i know how it functions but would very much like a manual, so if you know where to find one please let me know!

    Thanks,
    Dennis
    Attached Thumbnails Attached Thumbnails img_4745.jpg   img_4746.jpg   img_4943.jpg   img_4944.jpg   img_5066.jpg  


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  3. #2
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    Here you can find the electronic schematic of the display unit (FA 70-3) with a list of component values.

    FA 70-3 circuit diagram 2.jpg - Google Drive

    FA 70-3 circuit diagram components.jpg - Google Drive
    Attached Thumbnails Attached Thumbnails fa-70-3-circuit-diagram-2.jpg   fa-70-3-circuit-diagram-components.jpg  

  4. #3
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    You said that the vibrator sled resistance is over 40M Ohms?
    The parts list says that it should be 60 Ohms. You must have a
    burned out coil or broken wire. What does the vibrator sled do anyway?

    If the photo sensor is just an light sensitive resistor which would be
    reasonable given it's age then you should be able to use an ohm meter
    to take your readings. No need for a fancy tube (valve) circuit.

    What does the photo sensor look like? A picture would help.

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    No, the vibrator sled measured 44.5Ohms and the photo conductive cell measured over 40Mohms. There seems to be some differance in values depending on what autocollimator you have.
    I will include a picture of the photo sensor, but its not really helpfull because its build in the autocollimator and not really visable. Also not easely removable without messing up the allignment.


    the photo sensor is on the bottom where the 2 big wires go to.
    img_4991.jpg

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    My back of the envelope calculations says that 33 volt DC is applied
    to the sensor through a 470K Ohm resistor. The signal from the sensor
    must have an AC result that is fed to a balanced amplifier tube V101.
    If you put 33 volts DC fed through a 470K Ohm resistor you will
    replicate the power from the circuit.

    The AC is likely to be the result originating from the vibrator mechanism.
    To read the result use some capacitor larger then .02 uF with a voltage
    rating over 50 volts. Connect that to your digital voltmeter and
    set it to read AC. The signal is likely to quite small but the tube
    circuit is nothing magic. It is only a single tube balanced amplifier,
    quite standard for the day.

    You should see the AC voltage go up and down as you adjust the autocollimator.
    What the reading means is dependent on the optical design of the device.
    I would expect a peak or a null when the alignment is correct, but
    I am just guessing here.

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    Thanks for the input! And you are correct. And with the help of some people from another forum i was able to get it to work and actually measure it with my oscilloscope. Ive attached some pictures that show the 50Hz input sine wave to the vibrator sled (yellow line) and the output of the LDR (blue line) changing with the change in reading on the autocollimator.

    I will work on this some more and keep you posted.

    img_5081.jpgimg_5082.jpgimg_5083.jpgimg_5084.jpg


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