
network package can only vary by 0.5%, R2 cannot be less than 10,049.5. As a
result, the output will be
INPUT
R2
R1 þ R1
¼ INPUT 0:4987
which is within 0.25% of the ideal value.
Multiple Input Control
In some cases a system will have multiple inputs. For example, you might be
controlling a telescope that is taking pictures of clouds. For some reason (perhaps
to protect sensitive optics coatings), you don’t want to aim the telescope at the sun
(Figure 11.3). In this case, one of the inputs would be the position of the sun,
probably determined by the date and time of day. You would also have as inputs
the telescope’s current position and the desired