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IOTA - Setup of Reflectometer

Notes from MGL and RMG; Created: July 2004

Courtesy of Bill Kindred at MMTO, IOTA occasionally uses their reflectometer to test the reflectivity of the siderostats. The following notes compile information on how to set up and use the reflectometer.

Hardware Setup

[reflectom.gif - Reflectometer setup]


  1. Turn on bulb power supply, set to a low voltage, turn on current to bulb (orange switch on supply), and increase voltage until current limited state (light over current on).
  2. Put detector assembly [3] into lamp opening [1] to adjust current meter scale for maximum sensitivity without saturation, i.e., adjust current to give reading near 1.999 in appropriate meter range. Bulb voltage should be 5.4 to 6.6V, current around 3.3A.
  3. Put [1] into fixture opening [2] and [3] into [4], adjust feet to get maximum signal, and record current meter (Ir).
  4. Put [3] into specular outlet [5] and record current meter output to monitor lamp output change with orientation (Iref).
  5. Move lamp & photo-diode assembly into holder [6] clamped at same orientation as in 3.
  6. Repeat measurement of 4.; if current meter output is different (due to lamp orientation), adjust "FINE" of power supply to recover same reading.
  7. With the lamp left in place in holder [6], put detector [3] into [1] and record current output for direct illumination (Ii).
  8. Then:
    Reflectivity = Ir / Ii
    Paper is a few percent - most of the light diffused; fresh aluminum is 91% at 550nm.