Patent ID: 7170596

Claim:
An atomic absorption spectrophotometer comprising: a self reverse type hollow cathode lamp; a photomultiplier tube; a preliminary measurement performer for measuring a strength of a signal L when a smaller current is supplied to the hollow cathode lamp and a strength of a signal H when a larger current is supplied while a voltage V applied between a cathode and an anode of the photomultiplier is changed; and an optimal voltage detector for detecting a value V0 of the voltage V at which a super ratio U is closest to unity under a condition that two values V1 and V0 of the voltage V are arbitrarily chosen so that a ratio of value H1 to value H0 of the signal H or a ratio of value L1 to value L0 of the signal L is a predetermined value, where the super ratio U is defined as a ratio of a first ratio L0/H0 to a second ratio L1/H1.