Advantech IDK-2108 Series User Manual page 36

Note 5: Definition of response time
The output signals of the photo detector are measured when the input signals are
changed from "Full Black" to "Full White" (rising time), and from "Full White" to "Full
Black" (falling time), respectively. The response time is the interval between 10% and
90% of the amplitudes. Please refer to the figure below.
Optical Optical
response response
IDK-2108 User Manual
%
Tf
100
90 90
White White
10 10
0 0
Black Black
28
Tr Tr
White White