Validation of a Low-Cost Electrical Conductivity Sensor against Gravimetric Reference Methods for Diesel Emission Monitoring

Particulate Matter (PM) emissions from internal combustion engines pose significant risks to human health and the environment, necessitating strict monitoring regulations. However, conventional measurement techniques, such as the gravimetric method, are time-consuming and lack real-time capabilities, while opacity meters often suffer from low sensitivity at lower particle concentrations. This study presents the development of a portable, low-cost instrument for the real-time measurement of PM in vehicle exhaust gas using an electrical conductivity analysis technique. The developed system comprises a sampling probe, a dilution unit to simulate atmospheric mixing, and a sensor chamber utilizing high-voltage electrodes to measure the conductivity changes caused by charged particles. To validate the system, experiments were conducted using a single-cylinder diesel generator operating under varying electrical loads (0, 1, 2, and 3 kW). The sensor performance was compared against the standard gravimetric (filter weighing) method. Experimental results indicated an excellent linear relationship between the sensor’s voltage signal and the mass concentration of PM collected on filters (r = 0.9313). At the maximum load of 3 kW, the sensor measured a concentration of 33.93 mg/m³, which closely aligned with the 30.67 mg/m³ obtained via the gravimetric method. The findings demonstrate that the developed electrical conductivity sensor provides a reliable, cost-effective, and rapid alternative for in-field inspection and continuous monitoring of diesel exhaust emissions