distance measure using ultra sonic sensor:::timming problem

[mangood]

hi

i found  a problem during making a distance measure system

the timming diagram of the ultrasoinc type SRF05 below

the problem as flow

after i send at leat 10 us

what will happen and when to start capture value from output???100 us or 25 us what is mean

i read this this VI https://decibel.ni.com/content/docs/DOC-3737  and he said::

 """after send 10 us we Wait for falling edge of Output echo or timeout after 18ms""

best ragards