Specifications

Doc Number: VIS-ANA-VER-01001-9002
Date: 27 May 2004
Issue: 5.0
Page: 60 of 80
Author: J. Delgadillo
Controls Preliminary Design Report Issue 5.doc
4.3 Tape Encoder Calculations
4.3.1 Azimuth Tape Encoder Calculations
Azimuth Tape Encoder Resolution
Tape Sitting Diameter: 1638mm
Tape Sitting Circumference: 1638mm * Π = 5,145.9288 mm
Graduation Distance 40 e-6 mm = 25 lines/mm
# of Encoder Lines 25 lines/mm * 5,145.9288mm
= 128,648.2192 lines
IK 320 Interpolation Factor 4096 counts/line * 128,648.2192 lines
= 526,943,105.8 counts
Encoder Resolution 360°/526,943,105.8 counts = 6.832 e-7 deg
= 0.0025 arc-secs
Azimuth Tape Encoder Accuracy
Encoder Accuracy of Graduation +/- 3 microns = +/- 0.003 mm
Encoder Tape Circumference 5,145.9288mm = 360°
= 0.070 °/mm
Encoder Accuracy (One Read-Head) 0.07 °/mm * 0.003 mm
= 0.00021 ° = 0.755 arc-sec peak
Encoder Accuracy (4 Read-Heads) = 0.755 arc-sec / 2 = 0.378 arc-sec peak
4.3.2 Altitude Tape Encoder Calculations
Altitude Tape Encoder Resolution
Tape Sitting Diameter: 1854mm
Tape Sitting Circumference: 1854mm * Π = 5,824.5128 mm
Graduation Distance 40 e-6 mm = 25 lines/mm
# of Encoder Lines 25 lines/mm * 5,824.5128mm
= 145,612.8195 lines
IK 320 Interpolation Factor 4096 counts/line * 145,612.8195 lines
= 596,430,108.7 counts
Encoder Resolution 360°/596,430,108.7 counts = 6.0359 e-7 deg
= 0.0022 arc-secs