Chilled Mirror Hygrometer

Moisture Control

Polymers require specific water content thresholds to prevent hydrolysis during melt processing. A chilled mirror hygrometer verifies that resin drying equipment removes adequate atmospheric humidity from the recirculating air stream before the pellets enter the extruder hopper. Excess moisture results in polymer chain scission that reduces the final tensile strength and optical clarity of the molded part.

Producers verify the performance of desiccant beds by testing the dew point of the air discharge at the start of every production shift.

Tooling Accuracy

Cavity surface temperature regulation depends on the suppression of condensation to prevent cooling circuit corrosion or surface finish defects on finished parts. When the mold temperature falls below the dew point of the surrounding production floor air, moisture collects on the metal faces of the tool. This contamination marks the plastic part and alters the surface friction coefficient.

Maintaining a room air dew point well below the target mold temperature ensures the tool remains dry throughout the injection cycle.

Calibration Standard

Optical detection systems provide a primary reference for certifying secondary humidity sensors used in industrial monitoring arrays. Metrology laboratories employ the cooled surface method to establish traceable humidity values because the technique rests on thermodynamic principles instead of empirical correlations. This instrument generates a stable verification environment that supports long term consistency across multiple manufacturing locations.

The equilibrium between the condensed phase and the vapor phase defines the dew point temperature with physical certainty.