Process and pressure calibration verifies the measurement accuracy of the pressure or flow rate of enclosed systems like pipes, test valves, transducers, and pressure transmitters. Calibrators and accessories test or enable testing of voltage, current, resistance and frequency to verify that process transmitters, electrical equipment, or test valves operate within acceptable parameters. Ultrasonic flowmeters and accessories emit an ultrasonic signal through a pipe to measure the velocity and calculate the flow rate of the liquid inside.