Laser gas analyzer

1 . A laser gas analyzer comprising:

a laser diode that irradiates a measurement target gas with laser light;

a light receiving unit including:

a photodiode that receives the laser light that has passed through the measurement target gas; and

a light emitting diode (LED) that irradiates LED light such that the LED light is received by the photodiode without passing through the measurement target gas; and

a processor that:

calculates a concentration of a component contained in the measurement target gas based on an amount of light of the laser light received by the photodiode, and

determines presence of failure of the photodiode based on an output of the photodiode that receives both of the laser light and the LED light, wherein

the laser diode intermittently irradiates the laser light,

the LED irradiates the LED light at a predetermined timing during a period in which the laser diode does not irradiate the laser light,

when the processor detects the LED light but not the laser light during the period, the processor determines that the light receiving unit is normal, and

when the processor does not detect either the laser light or the LED light during the period, the processor determines that at least the light receiving unit is abnormal.

2 . The laser gas analyzer according to claim 1 , wherein

the period includes:

a settlement waiting period during which settlement of an output of the photodiode is paused; and

a dark current measurement period for measuring a dark current, and

the LED irradiates the LED light during the settlement waiting period.

3 . The laser gas analyzer according to claim 1 , wherein the LED changes at least one of an amount of light of the LED light or a wavelength of the LED light.