JULABO FK25-HL / FK50-HL / FK89-HL High-Precision Temperature Calibration Bath

Overview

The JULABO FK25-HL, FK50-HL, and FK89-HL series are high-precision temperature calibration baths engineered for metrological traceability in accredited calibration laboratories, national metrology institutes, and quality assurance departments operating under ISO/IEC 17025, GLP, or GMP frameworks. These units employ a dual-zone thermal architecture—combining a high-efficiency immersion heater with a fully integrated refrigeration circuit—to achieve continuous, stable temperature control across an exceptional range of –90 °C to +200 °C. Unlike conventional heating-only baths, the FK-HL series features full-range active cooling capability, enabling direct ramp-down from elevated temperatures (e.g., +200 °C) without thermal shock or extended cooldown delays. The core design centers on a precision-machined overflow cylinder mounted concentrically within the bath chamber, which ensures laminar fluid recirculation and minimizes vertical and radial thermal gradients. This geometry—validated per DIN 12876-1 and aligned with the principles of ISO/IEC Guide 99 (VIM)—delivers uniformity and stability both at setpoint and during dynamic load conditions.

Key Features

• Triple-parameter VFD display showing real-time bath temperature (actual), user-defined setpoint, and reference sensor input—enabling simultaneous comparison against certified reference thermometers.
• Overflow-cylinder thermal homogenization system ensuring ≤ ±0.01 °C spatial uniformity and temporal stability over 30-minute intervals (per ASTM E1137/E1137M Annex A1).
• Robust refrigeration modules rated for sustained operation at cryogenic endpoints (–90 °C for FK89-HL), with compressor staging optimized for low-noise, low-vibration performance (<45 dB(A) at 1 m).
• Integrated safety architecture: dual independent high/low temperature limit alarms, low-fluid-level detection with automatic heater cutoff, and pressure-relief protected circulation loop.
• Modular bath cover with multiple standardized apertures (Ø10 mm) for concurrent calibration of up to six probes—including PRTs, thermistors, liquid-in-glass thermometers, and digital sensors—without cross-contamination or convection interference.
• Compact footprint with ergonomic side handles and vibration-damped feet; designed for benchtop integration in ISO Class 5–7 cleanroom-adjacent environments.

Sample Compatibility & Compliance

The FK-HL series supports calibration of contact-type temperature sensors conforming to IEC 60751 (Pt100/Pt1000), ASTM E1137, and DIN EN 60584 standards. Its fluid compatibility extends to silicone oils (up to 200 °C), low-viscosity heat-transfer fluids (e.g., Dowtherm J), and specialized cryogenic media (e.g., ethanol/methanol blends for sub-zero operation). All models comply with electromagnetic compatibility requirements per EN 61326-1 and carry CE marking under the EU Machinery Directive 2006/42/EC. The bath’s thermal performance documentation satisfies traceability requirements for DKD/DAkkS calibration certificates (available optionally with DKD-accredited Pt100 reference probes), and supports generation of uncertainty budgets compliant with EURAMET cg-18 and BIPM CCT-K9 guidelines.

Software & Data Management

While the FK-HL operates as a stand-alone instrument, its analog voltage output (0–10 V) and RS232 interface enable seamless integration with external data acquisition systems (e.g., LabVIEW, MATLAB, or MET/TEMP II). When paired with JULABO’s optional TRACAL software suite, users can log timestamped temperature readings with audit-trail metadata—including operator ID, calibration event type, and environmental ambient logs—for compliance with FDA 21 CFR Part 11 and ISO/IEC 17025 clause 7.7. All internal firmware revisions are version-controlled and support field-upgradable security patches verified via SHA-256 checksum.

Applications

• Primary and secondary calibration of resistance thermometers, thermocouples, and infrared reference sources in NMIs and DAkkS-accredited labs.
• Verification of thermal performance in pharmaceutical stability chambers (ICH Q1A–Q1E), autoclaves, and incubators per USP and ISO 13408-2.
• Thermal validation of process sensors used in bioreactor control loops, where drift correction requires sub-0.02 °C reproducibility over 72-hour hold periods.
• Reference standard maintenance for black-body cavity calibrators and radiometric transfer standards requiring stable boundary conditions.
• Research-grade thermophysical property measurement, including viscosity-temperature profiling of lubricants and polymer melts using coupled rheometry.

FAQ

What is the difference between FK-HL and standard FK models?
The HL variants incorporate enhanced refrigeration capacity, reinforced insulation layers, and a recalibrated overflow geometry optimized for metrological applications—resulting in improved uniformity (±0.01 °C vs. ±0.02 °C) and reduced drift under long-term static conditions.
Can the FK89-HL operate continuously at –90 °C?
Yes—when filled with certified low-freezing-point bath fluid and operated in a climate-controlled room (18–22 °C, RH <60%), the FK89-HL maintains stable operation at –90 °C for ≥16 hours with ≤0.015 °C peak-to-peak fluctuation.
Is external calibration certification included with purchase?
No—certification is optional and must be specified at order entry. JULABO offers DKD-accredited calibration (traceable to PTB) or CNAS-certified reports issued by China National Institute of Metrology (NIM), both delivered with full uncertainty budgets.
What fluid types are recommended for the full temperature range?
For –90 °C to 0 °C: 50/50 ethanol/water or specialized cryo-fluids meeting DIN 51587 specifications. For 0 °C to 200 °C: ISO VG 10–100 silicone oils compliant with DIN 51519. Mineral oils are not recommended above 120 °C due to oxidation risk.
Does the unit support automated calibration workflows?
Yes—via RS232 command protocol (SCPI-compliant) and analog output synchronization, enabling integration into automated calibration management systems such as MET/CAL or Fluke 9100.