EDM Sensitivity Analysis
A couple of weeks ago, I was conducting some checks in my basement to assess the sensitivity of my EDM. I have an old Leica DI2002 distomat mounted on a T-2002 instrument. This is the same instrument pairing that NGS uses to certify/verify CBLs. The only difference is that the NGS uses two DI2002 in their measurements.
I was checking two positions; one at 2.8414 meters and the other at 3.0554 meters (mean of 20 measurements to each position). The half wave length for the EDM is 3 meters. I checked the distance between the positions with a calibrated scale(0.2138 meters) and it showed that my distomat exceeds the published s.e. of 0.6 mm for distances below 100 meters (as compared to an interferometer).
The next day (without moving anything!) I checked the distances again and to my amazement got distances of 5.8427 and 6.2831 meters respectively. Before my shots I maximized the return signal of the EDM. I rechecked the distances with other prisms and got similar odd results
What the heck is going on?
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