These gauges are sampled at approximately 1 Hz.

Sample file format:
  yr mm da hhmm pos  vis  lum  ALv ALl pts
2008  4 17 1554    1   5039   0    0  6  145
2008  4 17 1600    1   5038   0    0  6  293
2008  4 17 1606    1   5903   0    0  6  303
2008  4 17 1612    1   5568   0    0  6  304
2008  4 17 1618    1   5579   0    0  6  294

where:
   yr = year
   mo = month
   da = day of month
   hhmm = time (UTC/GMT)
   pos = instrument position on concrete slab
   vis = visibility (m)
   lum = background luminance (cd/m^2)
   ALv = alarm status of visibility sensor
   ALl = alarm status background luminance
   pts = number of points averaged in 6-minutes