Immersion Circulators accurately heat, circulate, and safely control temperature of liquid in the bath within precise limits. Units feature precise PID temperature control, a bright digital LED display, overtemperature indicator light, pressure pump, and low-liquid level cutoff. Unique clamp-on feature allows all circulators to be securely fastened to recommended list of unheated and liquid calibration baths. The TU models offer higher temperatures, increased stability, and an RS-232 interface with TechneWorks software package. Optional flow coolers used in conjunction with immersion circulators, may be purchased to help cool liquid temperatures down to -35°C. These compact refrigeration units continually extract heat from the bath fluid as it flows through the cooler by means of a builtin heat exchanger.