DL181 1980s Wild Heerbrugg T2000 Theodolite Total Station Teardown
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- เผยแพร่เมื่อ 22 ก.ย. 2024
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In this video i take apart an electronic Theodolite from 1986. The Wild Heerbrugg Theomat T2000.
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Complex optical voodoo is for automatic leveling compensation: you need very accurate vertical "zero" and 2 bubble levels aren't good enough. Fluid will make "contour" and optoelectronics shall read the amount of correction with 1" arc precision.
Angle measurements are complex. The fixed part shall read simultaneously from the opposite side of the disk to reduce concentric errors. "Flying" disk compensates for the graduation error.
T2000 was a high precision instrument from a 100 years old company. T1000(!) was a "simpler" model introduced in 1985.
I remember back in the mid to late 80's I worked for a company than designed Hand Held computers. One of the things that they were used for was collecting data from theodolites. (The interface wasn't serial RS232, but something more akin to SPI by the way). I remember having to solve a problem with the interface, so had access to the theodolite which was similar to this one, but with the distancing attachment.
I reckon that the oil filled optical device, is all to do with the electronic levelling. I seem to remember that there was a calibration process to go through.
The theodolite was initially levelled the old fashioned way using the spirit levels. As part of the calibration you would then sight the theodolite to a prism. The theodolite was then rotated 180 degrees and the telescope flipped 180 degrees (hence the reason for the handle to be moved out of the way). You would then re-sight the prism. In effect you have delta calibrated the instrument, thus eliminating any errors in the manual levelling.
Back in the 1980 before the computers were built into the theodolites the HP-41C calculators where often used for collecting survey data in the field. It might have been mostly manual data entry, although there were data interfaces available for some theodolites.
In case you didn't know, the fluid inside the thing at 38:24 is ethylene glycol, it's used in a bunch of different optical things. It's not volatile but it is pretty toxic so y'know, be careful and stuff. And yes, I realise I'm like six months late telling you this haha.
I guess you figured out what the fluid was for, but if not: It's the level compensator. If the unit is slightly out of level, the fluid slants, and the optical path is reflected off of the surface of the fluid from underneath, and if the liquid surface changes angle it changes the optical path slightly thus compensating for slight tilt in the instrument.
Amazingly interesting insides. Really didn’t expect that.
I always wanted to take one of those apart !
Very interesting, & a great piece of engineering. Thanks Mark 👍
38:25
Ha! WTF? Optical fluid? These instruments are quite ingenious.
The non electronic ones have to have about the same optical paths, just without the overkill, as the electronic one is meant to be accurate to the centimeter level over a kilometer, so you need to have a very accurate reading of both azimuth and attitude, to get that sort of precision. You typically start off at a datum point on your plot, and then go along with a path that leads you back to the origin again, so that at the end, when you have completed it, you can have an idea as to the overall error in your measurement, as the angles and distances measured should come back, after doing the math, or having a computer do it in this case with the unit, to be within your error budget for the path.
If not, you have made a mistake somewhere, and simply have to redo the survey, so that the final error is negligible, giving confidence in the survey result. Part of surveying, making sure that you have not had a systematic bias, wrong data taken down, wrong measuring or equipment failure along the way. The newer versions of this now also come with a GPS receiver in them, along with a separate radio receiver, that is used with a known located GPS receiver that is broadcasting the difference in position of it's location, so that your theodolite can have it's location mapped down to miilimeter accuracy on the site, as a further check of the data. GPS might only be accurate within a meter, but differential use can easily get better, especially since the more modern receivers sample at the baseband frequency, instead of downconverting to 70MHz like the original ones, and can measure time to picoseconds, even with SA turned on. Provided both can see the same constellation they will remain in lock, giving you a very accurate position relative to the stationary unit, even if it's indicated position is varying by meters with time.
This was an interesting teardown, and ticked all the boxes...
*Retro (80s) tech.
*Old-skool MCUs and PROMs.
*Precision mechanics and optics
*Lots of bolts to take out.
*Something most people wouldn't normally get to see.
*Oil. lol
I genuinely predicted the oil to leak out, as I couldn't think of what else would be in there. lol
I thought it was maybe just a prism at first, but it seemed too hermetically sealed for that.
Reminds me a bit of the oil-filled lenses on the old CRT-based rear-projection TVs.
I think some of the optical voodoo might be that the oil and glass have a closely-matched refractive index?
Maybe it uses Total Internal Reflection in some way, too, so the glass (and oil) appear like a perfect mirrored lense to a certain wavelength?
I tore down a 1990s vintage Sony rear-projection TV many years ago after it started failing. As soon as I opened up one of the 3 separate R, G, B CRT projector assembly cylinders to take a look inside I instantly regretted it as oil spilled out everywhere.
@@glenslick2774
lol
I very nearly did that once, too, but then found a copy of the service manual, so I didn't end up opening the lenses.
I probably had the same 40" Sony set as you. I ended up giving it away on Freecycle around 2014, as we were moving house.
The guy who collected it looked VERY pleased with it, as he wanted it for his games room / man cave.
His girlfriend didn't look quite so please. lol
@@electronash Hard to find a list of Sony models from that timeframe to try to figure out exactly which one it was. It was 4:3 and at least 40-inch and no larger than 46-inch from what I can remember. As it had failed I couldn't give it away. I tore it down into pieces as that was the easiest way to get it out of the house. Lots of particle board cabinet to chop up plus the large mirror and lens, not too much for the actual electronics.
Oil maybe mechanical vibration damping and/or to get a particular refractive index
Temperature compensation for the optical path changing length with temperature, as you are using the diffraction change to increase resolution, so you need to have a compensation for length in there somewhere. Thus the oil to do this, it will have a tempco just right to offset the difference.
I did wonder if it was a mechanism to make it super sensitive to movement using something like the Schlieren effect.
@@DextersTechLab Doubt it, that long optical path with all the prisms already provides a lot of amplification of the fringes as the slits coincide, and the internal reflection off of the front of the glass is likely what is used, though the oil could be acting as an optical interface to disperse reflections off of the rear face, dispersing the light into the cavity to be absorbed. If it was not doing compensation I would think they would have used a front silvered glass instead, solving the problem. The last thing they would want is any sort of change in the optical path other than the slits crossing in the glass encoder.
Search for "kern dkm liquid compensator". You will find PDF file on swisstek site which explain it.
Thank you Jan!
@09:21 there's a sticker showing the date it was checked - 26 June 1986
Most overkill use for one, setting a gate rail. We padded it to be within 1mm of level all the way through the travel, mostly because my brother in law is a civil engineer, and had it with him for work, so was the perfect tool to use for the job. Was actually quicker than using a spirit level, and was also much more accurate. Didn't even have to extend the yardstick either, top was at the right height for the job.
I guess a simple laset gauge gets 99% way there?
Wild (now called Leica) from Heerbrugg in Switzerland. Correct pronunciation is the W spoken as V and the word rhymes with “tilt”.
Would have cost several thousand new, not tens of thousands. But then a car also cost several thousand back then.
Top quality, evident by much lower operator stress after hours of use - particularly eyes.
They were really pragmatic in designing these and therefore significant damage (such as being hit by an excavator) would be repairable.
I am watching this video again because I did just order a Pentax PTS-II 05, more modern instrument and with built-in telemeter !
38:24 Release the schmoo!
i have seen that solder mask material before, but i have never seen such a strange crossing trace layout like that
Skip to 7:30 for the actual tear down.
I've never seen such a thing from the inside either.
I'm looking for a T 2002 Wild Total Station
Thanks a lot, I always wonder how these are working, I was expecting some high precision encoders but not quite this.. I never saw some fluid optics except for that focusing water "droplet", this is indeed some optics voodoo :D
I can only guess that the refraction index of that oil is very important and maybe the same as the glass for some funky optical behavior ;)
Thank you so much. I have problem That the lower plate can not levelled. Because 2 Rollers not moved
Cool, always did wonder what was in one of these things. Now I know :D Thanks
Good explanation
Really advanced device for the time
Enjoyed that thanks :)
always wondered what was in one of them.
10:19 That mini screwdriver and bit set looked ace. Mind if I ask where you got it?
Maybe the fluid stuff is a gravity vector detector (A.K.A. a level.) : ) A bubble may have been involved, but you let it get away. I see level indicators on the base, but they're probably just to get you close.
Stubby Phillips: I suspect you are right about it being a level however my guess is that it wasn't a "bubble" but rather the chamber was only partially filled with fluid. The two optical paths were for X/Y axis and measured the internal reflectance off the surface of the fluid (staying within the "critical angle" of the fluids optical properties). When setup correctly, the reflectance (off the oil surface) between the emitter and detectors (x/y) would be maximized when the unit was perfectly level.
@@ScientificSolutions I bet you're right. I guess now there's no point trying to figure out where the bubble went when it fell out .
The light reflects off and changes direction in exactly the amount that the device is non-level. Thus, it can behave as if it is level, even if it isn't.
could the fluid chamber be for thermal compensation?
or/and atmospheric pressure
Nice opening titles :-)
Yea, it's great to have the Ramcorder working again!
15:53 - That is super weird PCB... 38:40 - Interesting, they are using some kind of oil with optics, for what reason? To keep things cool, lubrication or to change the optical characteristics? We'd never know... This is the most advanced craziest optical device I have ever seen, makes no sense lol
I have a T2002 that needs servicing you interested?
No, sorry!
Are you going put it back together?
No, it was a one-way teardown.
friend I am a young student I have a gps leica 530 I beg you to help me with a copy of ski pro 2.5 or earlier and with a copy of the gps530 emulator I live in Nicaragua thanks friend.
More like Wild Heerbrugg T2000 Theodolite destruction....
Wild... That sounds disgusting. Read the company name correct. Pronounce in German, not English!!!
Hah... Try mount it back and it will not function. All you did - destroyed this rare high-precision instrument. It lost all value as museum piece.
Dude, the ads in the middle of the video are lame. You have a job, right?
Ads are always lame mate, but they pay and help.