Found this image (Pentax, not Nikon)--I'm assuming that what I'm seeing move is the filter noted on the left side? 
Nikon C-100
http://www.ebay.com/itm/Nikon-C-100-Total-Station-/391524966439?hash=item5b28b4e027:g:R~wAAOSwZVlXo-ax
Nikon NPL 350 Prsimless:
http://www.ebay.com/itm/Nikon-NPL-350-Prismless-Total-Station-/222208924937?hash=item33bcaf1d09:g:B1YAAOSwnQhXoo~D
And, if you don't mind topcon, these are good guns.
http://www.ebay.com/itm/TOPCON-GTS-3-TOTAL-STATION-TRANSIT-/271887060616?hash=item3f4dbb4e88:m:m1yn8HDIjDvxPlSjt5voeWQ
slyck, post: 385348, member: 11966 wrote: I'm an electrical engineer by degree, so there's at least a chance that I could troubleshoot and potentially fix the issue, if I just understood the detailed principle of operation.
That does make a world of difference. Since you're a double E maybe we should start by asking if you've removed the lens cover?
Slyck - please don't take this personal,,it's just my dark sense of humor and the level of love and affection I have developed over the years for engineers...
laugh with us buddy! 😉
paden cash, post: 385416, member: 20 wrote: That does make a world of difference. Since you're a double E maybe we should start by asking if you've removed the lens cover?
Slyck - please don't take this personal,,it's just my dark sense of humor and the level of love and affection I have developed over the years for engineers...
laugh with us buddy! 😉
Maybe that's the issue! It seemed rather dim so I tried pointing it at the sun for a while...:D
slyck, post: 385419, member: 11966 wrote: Maybe that's the issue! It seemed rather dim so I tried pointing it at the sun for a while...:D
Seriously I can appreciate your confidence level to get in there and fix it. From my experience it is a whole lot easier to send them to the shop. That is such a unique circumstance that I can't help but think there's a good bench tech that might have some insight. The trick is finding one that has experience on your particular model. Good luck and keep us informed.
"Distances are determined by timing the infra-red signal from its emission until it is reflected and sensed. This is done actually by measuring the elapse time. I'm betting there is an internal battery on your mother board that is strictly for clocking the signal...and its shot. Anything else in my mind would return an error code on the display. Check with someone that can tell you if there is an internal battery on the mother board. Scotch out..."
I don't think that is exactly correct. Light of any kind is very fast. Atomic clocks would be necessary to measure the incredibly small elapsed times for any measurement commonly performed in surveying. My understanding is that light beams of known frequencies are projected to the prism. The distance meter can determine how "out of phase" the return signal is. Sort of like tuning a radio to a certain frequency. Only, in this case, the frequency remains constant and the displacement is measured.
2 or 3 lights, modulated. Slightly out of phase. Measure phase difference, divide by 2. There is the distance.
Nate
PS Foshee is right.
KevinFoshee, post: 385482, member: 8314 wrote: Light of any kind is very fast. Atomic clocks would be necessary to measure the incredibly small elapsed times for any measurement commonly performed in surveying.
Long-range scanners use time-of-flight technology, so they must have figured out the clock thing without going atomic (or maybe they are atomic). The clock uncertainty is the reason TOF scanners aren't quite as accurate as phase-based models.
I have to admit I don't have direct knowledge of any particular EDM technology. But in general they rely on a radio frequency modulation of the IR light beam. They measure time of flight indirectly by comparing the phase of the RF modulation (not the light phase itself). The RF modulation frequency is stepped to move from a coarse RF wavelength to fine RF wavelength, with the finest being a few meter wavelength (many older models used 10 meters, some 5 meters, and perhaps shorter on newer models). The coarse wavelength measurements resolve the ambiguity of 10-meter (or finer) multiples, and the final measurement is the fraction of the 10 meters indicated by its RF phase.
The filter would be used to normalize the strength of the return from near vs far targets, so that the photo detector can always operate in a reasonably narrow range. I have no idea why there is a chopper, as it doesn't have a place in the scenario I just described, and I wonder if that is part of an ambiguity resolution scheme. But the time of flight for a 1-mile target range is around 1/100,000 second and too fast for mechanical devices.
