Hanuo HN-20M Precision Standard Circulating Bath

Overview

The Hanuo HN-20M Precision Standard Circulating Bath is an engineered thermal reference system designed for metrological calibration and high-fidelity temperature-controlled experimentation. It operates on a dual-mode thermoregulation principle—integrating Peltier-based refrigeration with high-efficiency resistive heating—to maintain stable, uniform thermal fields across its full operating range of −20 °C to 95 °C. Its core architecture follows ISO/IEC 17025-compliant design principles for reference-grade thermal equipment, emphasizing minimal thermal drift, low spatial gradient, and repeatable setpoint response. The unit serves as a primary thermal source in national and industrial metrology laboratories, particularly for the calibration of reference thermometers—including mercury-in-glass standards (Class I/II), Beckmann differential thermometers, Pt100 industrial resistance thermometers, and Cu–Constantan standard thermocouples—under controlled environmental conditions.

Key Features

• Stainless steel brushed-finish construction (inner tank and outer casing) ensures corrosion resistance, mechanical durability, and compliance with cleanroom-compatible surface requirements.
• PID-based digital temperature controller with adaptive tuning delivers ±0.01 °C stability over 30-minute intervals and ≤0.01 °C spatial uniformity within the central working zone (Ø100 mm × 300 mm).
• Optimized internal circulation system provides laminar, low-turbulence fluid flow—critical for minimizing thermal stratification during extended calibration cycles.
• Dual-fluid compatibility: validated operation with anhydrous ethanol at sub-zero temperatures and deionized water above 30 °C, enabling seamless transition across the full thermal span without hardware modification.
• Thermal recovery performance: ≤10 minutes to stabilize at target temperature following a 10 °C step change, supporting efficient multi-point calibration protocols.
• Compact footprint (420 mm × 360 mm × 650 mm) and integrated work-surface height design facilitate integration into constrained metrology benches or ISO-classified lab environments.

Sample Compatibility & Compliance

The HN-20M accommodates immersion-type temperature sensors up to Ø95 mm in diameter and 280 mm in length. Its open-bath configuration supports simultaneous calibration of multiple probes using standardized probe holders compliant with ASTM E74-22 (Standard Practices for Calibration of Force-Measuring Instruments) and JJG 229-2010 (Chinese National Verification Regulation for Thermometers). The bath meets essential requirements for GLP and GMP-aligned thermal validation workflows, including traceable temperature logging, audit-ready parameter history, and environmental condition monitoring (ambient temperature <30 °C required per specification). While not intrinsically certified to IEC 61000-6-3 or FDA 21 CFR Part 11, its analog/digital control interface allows integration with validated third-party data acquisition systems supporting electronic record integrity and user access controls.

Software & Data Management

The HN-20M operates via a front-panel digital controller with real-time display of setpoint, measured bath temperature, and system status indicators (heating/refrigeration active, circulation ON/OFF, fault alerts). Optional RS-485 or analog 4–20 mA output interfaces enable connection to external SCADA platforms or LIMS systems for automated data capture. When paired with calibrated NIST-traceable reference thermometers and time-stamped acquisition software, the system supports generation of calibration certificates compliant with ISO/IEC 17025 Clause 7.7 (Results of Testing and Calibration). All temperature logs retain timestamp, operator ID (via external login), and environmental metadata—enabling full traceability for internal audits or accreditation body review.

Applications

• Primary and secondary calibration of liquid-in-glass, resistance, and thermocouple thermometers in national metrology institutes and accredited calibration labs.
• Thermal validation of analytical instruments requiring stable thermal input—e.g., viscometers, densitometers, and thermal conductivity analyzers.
• Reference-source provision for material property testing (e.g., coefficient of thermal expansion, specific heat capacity) under controlled isothermal conditions.
• Stabilization of optical components, laser diodes, or photodetectors during precision alignment or spectral characterization procedures.
• Support of pharmacopeial methods (USP , EP 2.2.43) requiring defined thermal equilibration steps prior to dissolution or stability testing.

FAQ

What temperature media are compatible with the HN-20M, and how are they selected?

Anhydrous ethanol is specified for operation below 30 °C; deionized water is recommended above 30 °C. Media selection must follow viscosity, flash point, and thermal expansion constraints outlined in the user manual.
Is external circulation supported?

No—the HN-20M features internal recirculation only. For external loop applications, consider the HN-20MX variant with dual-port manifold and pressure-rated pump.
Does the unit include NIST-traceable calibration documentation?

Factory calibration is performed using ISO/IEC 17025-accredited reference standards; a certificate of conformance is supplied. Full NIST-traceable calibration requires optional on-site service by an accredited provider.
What maintenance intervals are recommended for long-term stability?

Biannual inspection of coolant level, circulation filter, and PID tuning parameters is advised. Stainless steel surfaces require cleaning with pH-neutral, chloride-free detergents to prevent pitting corrosion.
Can the HN-20M be integrated into a networked laboratory automation system?

Yes—via optional RS-485 Modbus RTU or analog 4–20 mA output, provided the host system implements appropriate isolation and grounding per IEC 61000-6-2.