Patent ID: 7469196

Claim:
A method for measuring a characteristic of a transfer circuit which transmits a signal and comprises an electrical signal sending section that transmits a sending signal, a current to light converting section that converts the sending signal to an optical signal, an optical signal transmitting section that transmits the optical signal, a photo-electric converting circuit that converts the optical signal to an electrical signal, a level measuring section that compares the intensity of the electrical signal output from the photo-electric converting circuit and a predetermined reference level to detect a data value of the electrical signal, an electrical signal receiving section that detects a data value of the electrical signal, and a timing controlling section that controls latch timing at which the electrical signal receiving section detects the data value of the electrical signal, the measurement method comprising: a comparing step of comparing the data value of the electrical signal received by the electrical signal receiving section with a predetermined expected value; a setting controlling step of sequentially changing the reference level and the latch timing with a predetermined resolution; and a result storing step of storing a comparison result in said comparing step for each the reference level and the latch timing.