Loveland, Colo.— Working unattended for up to 60 days at a time, SP 510 samples water every two minutes, measuring water hardness colorimetrically. When hardness exceeds a predetermined limit, the unit triggers an alarm. An integrated relay can also trigger automatic softener regeneration eliminating guesswork, risk, and cost of volume calculations. Calibration is a six-minute process where an LED prompt guides the operator through each step and signals when successfully completed. Hach Co.