Askey offers you the option of a subscription for the number of recorders you need. Upon entering into the agreement, we ship your loggers, which are delivered individually calibrated and certified. We keep track of when these need to be replaced with new ones. One month before the expiration date you will receive the new shipment. The logger’s calibration certificate is always at hand because it is stored in the recorder. And all that for a price less than the annual calibration cost.