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Calibrating an auto level?
This is purely mechanical surveyor's level, for levelling only,
absolutely no electronics. A tiny mirror or prism , on a very constrained and damped pendulum, set in the optical path of a x28 telescope set on a spherical mount to a tripod, to get initial rough levelling by x-y spirit bubble, then the pendulum system corrects within the last +/-10 angle minutes of level. It is a Sokisha B2 probably decades old, working with good repeatability but poor direct levelling. Checking against levels off a lake it is about -27.4mm over 100m, but consistent on return legs and repeating. Requiring offsetting , for any non-balanced levelling, ie non-equal legs either side of the tripod. I've the user manual and the carry case contains the tools for adjusting the calibration but no blurb. Cannot find a technical manual for this or any other similar, different makes, of auto level. But I found where it looks like you adjust , by unscrewing (not obvious it unscrews) cover around the eyepiece. Anyone any ideas on how to do the adjustment, assuming I have a good long-leg sighting run to a staff. There are 4 brass set screws, holed to take the adjustment tools , arrayed around the eypiece. So far I've taken and recorded vernier calliper reading of each of the 4 set screw heads, across the diameter to the threaded boss diametrically opposite, plus 4 dots of paint. Would top and bottom ones adjust the vertical displacement? and would the process be -1/8 turn on one and +1/8 turn on the opposite other, measure the displacement at distance and reverse if going the wrong way and repeat until nearer 0 displacement on the staff at the relevent distance. Would the other pair of adjusters have to be slackened off ,1/8 turn say, while doing this , then finger-tip torque tightened back 1/8 turn , or at least balanced if not 1/8 turn available then. Its not possible to see how this adjusment mount is constrained, or not. Hopefully no threadlock on the set-screws or if there is, then overcome wiht a few seconds of soldering iron. |
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