The best (and most accurate) way to calibrate a pump is with a 'primary' calibration device. These devices include bubble meters/tubes, dry gas meters an piston calibrators including the Bios Defender, the Gilian Gilibrator, Zefon DigiCal and the TSI Primary Flow Meter. A rotameter flow meter may also be used, however it is considered a secondary calibrator and should be verified for accuracy against a primary calibrator. Some pumps require specialized calibration devices. Please consult the owners manual of your pump to verify if any special calibration devices are required. If you need help regarding calibration, please contact your Zefon sales representative.