| 摘要 |
PURPOSE:To prolong the life of a lamp, by changing the discharge current of a lamp as a light source corresponding to the use sensitivity of an ultraviolet (UV) detector. CONSTITUTION:A lamp lighting circuit 12 is equipped with a constant current circuit 14 and a discharge current setting circuit 16. The circuit 14 receives set voltage from the circuit 16 at the discharge current setting terminal 18 thereof and the current flowing to a deuterium lamp 2 is detected by a current detecting resistor R1 and a constant current is supplied to the lamp 2 through a diode D so as to make the voltage drop Vr of the resistor R1 equal to set voltage. A discharge current set value by the circuit 16 is automatically changed with the range of a detection system changed over by a range change-over circuit 40. By this method, because the life of the lamp 2 is prolonged and the lamp current is made large only at the time of high sensitivity use, a current equal to or more than a rated current is caused to flow without shortening the life of the lamp to enable the use of a detector in a small noise level state. |
