The HF Scientific CLX residual oxidant and chlorine monitor features user-selectable features and innovative design. The CLX features cycle times adjustable from 110 seconds to 10 minutes, 4-20mA and Modbus outputs that can control feed pumps and user-settable alarms, resulting in low operating and maintenance costs. A new flow-through design maintains cuvette cleanliness and allows for viewing of optical operations. The strong, shatterproof case that opens to facilitate reagent replacement also allows easy access to all service functions, reducing maintenance time. Unattended operation and low chemical usage equates to low operating cost.