Semi-open atmospheric ammonia concentration detection system and method for measuring atmospheric ammonia concentration

A semi-open atmospheric ammonia concentration detection system, comprising:

• a case with at least one ventilation hole;
• an ammonia concentration detector arranged in the case and configured to detect ammonia concentration, the ammonia concentration detector comprising:
• a quantum cascade laser configured to emit a laser beam and scan an atmospheric ammonia absorption line;
• a reference component that forms a reference path, the reference component comprising a high-concentration ammonia reaction cell and a reference photodetector;
• a measurement component that forms a measurement path, the measurement component comprising a first mirror, a first concave mirror, a Herriott cell, a second concave mirror, a second mirror, and a measurement photodetector;
• a beam splitter configured to split the laser beam emitted by the quantum cascade laser into a first beam passing along the measurement path and a second beam passing along the reference path, the first beam passing through the first mirror, the first concave mirror, the Herriott cell, the second concave mirror, and the second mirror in sequence;
• and
• a data processor;
• wherein:
• the measurement photodetector is configured to detect and process a measurement signal of the ammonia characteristic absorption line;
• the reference photodetector is configured to detect and process a reference signal of the second beam passing through the reference path;
• the data processor is configured to acquire a direct absorption concentration of a detected gas based on the measurement and reference signals;
• a fan arranged in the case configure to accelerate a flow speed of the gas entering and exiting the ventilation hole when turned on;
• and
• a power supply arranged in the case, electrically connected to the ammonia concentration detector and the fan, and configured to supply power to the ammonia concentration detector and the fan.