C

4

F

7

N gas mixture is an environmentally friendly insulating alternative gas to SF

6

for new electrical equipment. C

4

F

7

N gas mixture

in case of being used as an insulating gas in high-voltage equipment

has similar problems with SF

6

equipment

and the quality of the gas mixture affects normal operation of the equipment. The C

4

F

7

N gas mixture

in case of moisture exceeding the limit

is likely to occur such problem as reduction of insulation performance of equipment due to discharge. It is therefore particular important to develop the operation

maintenance and detection device for the use of C

4

F

7

N gas mixture. In this paper

the quantitative detection technology of micro moisture content in C

4

F

7

N by tunable laser

infrared absorption spectroscopy is mainly studied. The spectroscopy theory of the tunable laser

the principle of harmonic detection and the infrared absorption characteristics of moisture are studied

and the influence of C

4

F

7

N as background gas on the accuracy of micro moisture detection is introduced. Then

the TDLAS structure design

hardware design and type selection are introduced. The DFB laser is used to design and manufacture the photoelectric conversion module

the light source driving module

the infrared multiple reflection pool

the circuit as well as software parts. The micro-moisture detection device for C

4

F

7

N gas mixture is developed based on the tunable laser

which removes the influence of interference components

improves the accuracy of micro moisture detection and can detect a low limit down to 1 μL/L. The performance results of the device show that it meets standard requirement

has high accuracy of quantitative detection of micro-moisture

and is beneficial to the correct judgment of the operating state of the equipment.