Process monitoring test instruments assess, maintain, build, and calibrate process systems to improve efficiency and pinpoint issues before they cause downtime. Analog panel meters are typically used when relative change is a critical factor in a process. They have a moving needle and a numbered dial that displays measurement data, such as temperature, speed, pressure, and current. Digital panel meters precisely measure electrical flow conditions, such as voltage and current, and display the results on an easy-to-read LCD or LED screen. Process calibrators, process loop calibrators, and temperature calibrators are portable, handheld instruments that calibrate and measure values in instrumentation to identify faults in process applications. Ultrasonic flow meters use ultrasonic waves to detect and measure the speed of liquid or gas inside a pipe without having to break it open.