The PMU project originally aimed to develop a relatively low-cost and portable research instrument for continuous measurement of NH₃ and CO₂ concentrations in Concentrated Animal Feeding Operations (CAFO), particularly focusing on poultry facilities (Xin et al., 2002).

The development of the PMU was motivated by the issue of the sophisticated, high-cost, and less portable methods of measuring NH₃ and CO₂. Therefore, the PMU was designed to produce comparable results to the sophisticated and expensive measurement methods. The PMU project evolved over the years in three generations, with each subsequent generation striving to make the PMU more robust.

The renovated PMU latest version (PMU4) introduces the Internet of Things (IoT) architecture to the PMU system.

PMU 1

2002

First generation prototype by Dr. Hongxwei Xin

PMU 2

2005

Second generation prototype by Dr. Richard S. Gates

PMU 3

2016

Third generation prototype by Boyu Ji