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Angular positioning

For angular positioning measurements an angular optics together with rotary encoder should be used. Necessary components are:

Angular positioning measurements require usage of the rotary encoder RE1 together with optical elements IK1 and RK1. The Rotary Encoder is to be mounted precisely in the center of rotation of the measured axis. On the Rotary Encoder there is mounted the Angular Retro-reflector RK1. Outside the Rotary Encoder there are placed the Laser Head and the Angular Interferometer IK1 as shown in the figure above.

The Angular Positioning measurements are performed with the use of two measurement instruments working together: RE1 and the Laser Head. The coarse value of the angle is given by the rotary encoder RE1. The encoder has seventy two distinct steps (each 5 degrees) defined with the accuracy of 0.5 ’’ or 1 ’’ depending on the chosen version. Because of the internal construction of the encoder, rotation between positions requires lifting up the top part of the encoder during movement. The lifting up process is driven automatically by the laser but requires careful beam alignment. For this reason it is sometimes better to take off during measurements the diaphragms from the RK1.

The laser head has two functions during the measurements: it controls and drives the whole process and at the same time measures the fine value of the angle in the range of +/- 5 degrees with the resolution of 0.01 ’’. The measurements are performed with the use of angular optics – IK1 and RK1 and mechanical mounts.

 

The laser communicates with the Rotary Encoder wirelessly over the same radio interface that is used for communication with the environmental sensors. The presence of the powered on encoder is detected by the laser automatically and signalized by the yellow color on the Rotary link field in the Status bar.

Proper rotary measurements are possible only if the laser sets up measurement link with the encoder. During the link set up procedure the wireless link quality and the optical signal strength are tested. The laser tries to drive the table to rotate -5 degrees, then +10 degrees and then -5 degrees. If all the tests are succeed, then the link with the encoder is set (Rotary link field in the Status bar changes to green) and the measurements are possible.

During measurements the laser monitors the current rotation of the RK1 element. If the measured angle is grater than 5 degrees then the rotary encoder RE1 is rotated one step (i.e. 5 degrees) in the reverse direction, so that the angle measured by the angular optics is always inside +/-5 degrees range.