Hanuo HN-20A Precision Metrology-Grade Constant Temperature Bath

Overview

The Hanuo HN-20A Precision Metrology-Grade Constant Temperature Bath is a laboratory-grade thermal reference system engineered for calibration and verification of temperature-sensitive metrological instruments. It operates on the principle of active dual-mode (refrigeration + heating) thermal regulation within a thermally insulated bath chamber, maintaining a highly stable and spatially uniform temperature field across its 23 L working volume. Designed specifically for primary and secondary calibration tasks—including fixed-point verification of standard mercury-in-glass thermometers (Class I/II), Beckmann differential thermometers, industrial platinum resistance thermometers (PRTs), and certified Cu-Constantan thermocouples—the HN-20A meets the foundational thermal stability requirements outlined in ISO/IEC 17025:2017 for accredited calibration laboratories. Its −20 °C to +100 °C operating range, combined with ±0.01 °C temperature stability and uniformity, enables traceable temperature assignments under controlled ambient conditions per ASTM E77, ISO 5725, and JJG 50–2019 (Chinese National Verification Regulation for Liquid-in-Glass Thermometers).

Key Features

• High-resolution digital display with 0.001 °C readability, supporting real-time monitoring and manual verification logging.
• PID-based closed-loop temperature controller with adaptive tuning, minimizing overshoot and ensuring rapid thermal equilibration after setpoint changes.
• Internally recirculated bath design with optimized fluid dynamics to eliminate thermal stratification; uniformity verified at multiple axial and radial probe locations per ISO/IEC 17025 Annex A.3.
• Dual-function thermal system integrating high-efficiency immersion heating elements and a hermetically sealed refrigeration compressor—enabling seamless transition between sub-zero and elevated temperature regimes without external coolant or chiller dependency.
• Integrated safety architecture including independent over-temperature cut-off (hardware-latched), compressor thermal overload protection, and current-limiting circuitry compliant with IEC 61010-1:2010 for laboratory electrical equipment.
• Stainless steel bath vessel with precision-machined Φ150 mm × 480 mm vertical access port, accommodating full-immersion calibration of long-form reference sensors and multi-probe fixtures.

Sample Compatibility & Compliance

The HN-20A is validated for use with anhydrous ethanol as the primary working medium—selected for its low vapor pressure, wide liquid-phase range, and minimal thermal expansion coefficient between −20 °C and +100 °C. It supports full-immersion calibration of length-standardized thermometers up to 500 mm, PRT probes with diameters ≤8 mm, and thermocouple assemblies conforming to IEC 60584-2 tolerance classes. The system satisfies environmental control requirements for temperature calibration laboratories operating under GLP and GMP frameworks. All thermal performance specifications are verifiable via internal PT100 reference sensor and externally traceable to NIM (National Institute of Metrology, China) or EURAMET calibration certificates. Documentation includes factory calibration report, conformity declaration per GB/T 19001–2016 (ISO 9001), and CE-marked electrical safety certification.

Software & Data Management

While the HN-20A operates as a standalone analog-digital hybrid instrument, its RS-232 serial interface (optional USB-to-serial adapter) enables integration with third-party data acquisition platforms such as LabVIEW, MATLAB, or custom Python-based logging tools. Temperature readings can be streamed at configurable intervals (1–60 s) for time-series analysis, statistical process control (SPC), and audit-ready record generation. When deployed in regulated environments, the system supports 21 CFR Part 11-compliant workflows when paired with validated software that enforces electronic signatures, audit trails, and role-based access controls. Raw thermal logs include timestamp, setpoint, measured value, deviation, and status flags (e.g., “HEATING”, “COOLING”, “STABLE”).

Applications

• Primary and secondary calibration of liquid-in-glass thermometers per JJG 130–2011 and ISO 17025 Clause 6.4.3.
• Verification of industrial Pt100/Pt1000 RTDs against ITS-90 reference functions using fixed-point interpolation methods.
• Thermal validation of environmental chambers, incubators, and sterilization autoclaves via sensor mapping protocols.
• Material testing support for coefficient-of-thermal-expansion (CTE) measurements requiring stable thermal soak conditions.
• Reference source for heat transfer coefficient determination in convective fluid studies.
• Quality assurance in pharmaceutical manufacturing where thermal excursions must remain within ±0.1 °C during stability testing (ICH Q5C).

FAQ

What working fluids are compatible with the HN-20A besides anhydrous ethanol?
The bath is validated for anhydrous ethanol only. Substitution with water, silicone oil, or glycol mixtures invalidates thermal uniformity and stability specifications and may compromise refrigeration system integrity.
Is the HN-20A suitable for ISO/IEC 17025 accreditation audits?
Yes—provided users maintain documented evidence of periodic verification (e.g., annual thermal mapping, sensor calibration traceability, and controller linearity checks) per Clause 6.4.6 of ISO/IEC 17025:2017.
Does the unit include a built-in reference thermometer?
No. A certified reference PT100 or SPRT must be used externally for calibration verification; the internal sensor serves only for closed-loop control.
Can the bath operate continuously at −20 °C?
Yes, but ambient temperature must remain below +25 °C and relative humidity below 60% to ensure compressor longevity and condensation-free operation.
What maintenance is required for long-term metrological reliability?
Biannual cleaning of the evaporator coil and bath chamber, annual recalibration of the internal temperature sensor against a traceable standard, and replacement of anhydrous ethanol every 12 months or when hygroscopic absorption exceeds 0.1% w/w.