Phase testers are devices used to detect and measure the phase angle between electrical signals, providing accurate and reliable phase measurements. They are used in applications such as power system monitoring, electrical testing, and communication systems, ensuring precise phase detection and alignment. Phase testers offer features such as high precision, digital displays, and easy operation, making them essential for maintaining the performance and safety of electrical systems. Their ability to provide reliable phase measurements makes them valuable for optimizing electrical system operation and ensuring safety.