The following example is a good way to understand these principles. How accurately can you measure the depth (i.e., Signal) of the ocean at two different locations? The first location is near the shore where the depth is about two feet; the second location is further out where the depth is about one hundred feet. Let us further assume that the water is choppy (Noise) with disturbances of two feet, peak to trough. Exactly how deep is the water when you are standing in two feet of water with two-foot, peak-to-trough waves rolling by? At any instant in time, two-foot waves add about a 50% uncertainty to your measurement accuracy.
Now sail out to water that is 100 feet deep. The same two-foot waves only introduce a 1% uncertainty, relative to the much deeper water. Likewise, the instrument noise-floor is significantly more dominant when measuring small signals versus large signals. The instrumentation noise floor in the GeneChip Scanner 3000 is below the expected biological noise-floor of the array itself.
Reduced Measurement Offset
While noise limits the ability of an electrooptical measurement system to accurately quantify low-level signals, offset reduces the available dynamic range of the system. Offset is the average value returned by the acquisition system with n