An Oil Tester is a specialized electrical testing device used to check the quality and condition of insulating oils, especially transformer oil. It measures important properties such as dielectric strength, moisture content, contamination level, and overall oil health. In Bangladesh, Oil Testers are widely used in power stations, industries, and electrical maintenance work to ensure transformers and other high-voltage equipment operate safely. Transformer oil plays a key role in insulation and cooling, so regular testing is very important for system reliability. By detecting oil degradation or contamination early, an Oil Tester helps prevent electrical failures and equipment damage. Overall, it is an essential tool for maintaining electrical safety and performance.