An innovative portable monitoring unit for air quality in animal housing

microprocessor;data acquisition and control system;ammonia;carbon dioxide;concentration measurement

Ji, Boyu

关键词: microprocessor;    data acquisition and control system;    ammonia;    carbon dioxide;    concentration measurement;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/78528/JI-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The Portable Monitor Unit (PMU) is a system developed to measure ammonia (NH3) and carbon-dioxide (CO2) concentrations in CAFOs. However, the NH3 electrochemical (EC) sensor used in the existing PMU design has become obsolete; moreover, the original PMU design required a substantial amount of manual work for system setup and data post-processing. Therefore, the objective of this project was to upgrade the PMU with a new NH3 EC sensor and data acquisition and control system. In this project, four different models of NH3 EC sensors were evaluated for suitability in this application. One, the HONEYWELL EC FX sensor, was selected as the replacement. It demonstrated sufficiently fast response time to a step change in NH3 (60 s to reach 95% equilibrium) and reasonable listed accuracy (±5 ppm at 100 ppm full scale). Other evaluation criteria were nonlinearity (maximum 3.8 ppm with 54 ppm NH3 reference gas), uncertainty (about ±3 ppm) and drift error (maximum 4.8 ppm within 48 h).The sensor was deemed to be acceptable based on these evaluations, and a multi-point calibration and 48 h laboratory evaluation with 24.3, 54 and 99.3 ppm NH¬3 reference gas. The new sensor was utilized in the upgraded PMU system with 5.5 min sampling (3 min line purge + 2.5 min measurement) and 54.5 min sensor purge. An Arduino microprocessor (Mega 2560) with extended function modules (Wireless SD shield, Real Time Clock shield, Relay and LCD screen) provided functions including sampling control, system auto-reset, data centralization, real-time data processing and wireless data transfer. The upgraded PMU (PMU III) was evaluated in two field tests at a commercial laying hen facility, and the system successfully implement the upgraded functions. The system was modified between the first and second field test mainly to improve the virtual timer and real-time data processing algorithm in its program. With the modified PMU III system, the data acquisition system uses a real time clock, so that during the measurement, real-time processing can provide reasonable results compared to the post-processing with consistency of 94%. A 12 h laboratory evaluation was performed to the NH3 sensor after the field tests for comparing the consistency with the prior 48 h laboratory evaluation, and thus demonstrated the reliability (maximum difference 2.6 ppm with 24.3 ppm NH3 reference gas) of the sensor during the field test.