A testing machine may perform breakdown voltage measurement, moisture analysis, dielectric dissipation factor or power factor, resistivity, and sometimes basic acidity screening depending on the instrument. Dedicated laboratory systems also perform dissolved gas analysis and furan analysis. Field kits focus on rapid screening to decide whether filtration, regeneration, or laboratory testing is required. The function is to quantify oil condition, detect contamination, and support maintenance decisions before defects progress to insulation failure. Proper calibration, clean sample handling, and adherence to test standards are essential for meaningful results.