JULABO FK31-SL High-Precision Temperature Calibration Bath

Overview

The JULABO FK31-SL High-Precision Temperature Calibration Bath is an ISO/IEC 17025-aligned thermal reference system engineered for metrological traceability in calibration laboratories, pharmaceutical QC environments, and national metrology institutes. It operates on the principle of forced-convection liquid temperature stabilization using a dual-mode (heating/cooling) thermoregulation architecture with integrated refrigeration and high-efficiency immersion heating. The bath employs a concentric overflow cylinder design—fully submerged within the main reservoir—to eliminate thermal stratification and ensure spatial uniformity across the entire working volume. This geometry, combined with SmartPump variable-speed circulation and ICC (Intelligent Control Concept) adaptive PID tuning, delivers long-term stability of ±0.01 °C and short-term fluctuations below ±0.005 °C at any setpoint between −30 °C and +200 °C. Its DIN 12876-1 Class III (FL) classification certifies suitability for flammable liquids, supporting use with silicone oils, ethylene glycol/water blends, or specialized low-viscosity calibration fluids.

Key Features

• VFD + backlit LCD dual-display interface showing real-time bath temperature, setpoint, and external reference sensor reading simultaneously
• Integrated ATC3 (Automatic Three-Point Calibration) function enabling in-situ verification and correction against certified reference probes
• TCF (Temperature Control Function) algorithm optimizing dynamic response during rapid ramping—e.g., cooling from +200 °C to −30 °C without overshoot or condensation-induced instability
• SmartPump technology automatically adjusts impeller torque and flow rate to compensate for viscosity changes across the full temperature range
• Full-featured safety architecture: overtemperature cutoff (user-definable threshold), low-fluid-level detection, dry-run protection, and audible/visual alarm escalation
• RS232 serial interface compliant with SCPI command syntax for integration into automated calibration workflows and LIMS environments
• Optional analog I/O module (0–10 V / 4–20 mA) supporting closed-loop control of auxiliary systems such as environmental chambers or test fixtures
• Pre-programmed 6-segment, 60-step temperature ramp sequences stored internally—no PC dependency for routine calibrations

Sample Compatibility & Compliance

The FK31-SL accommodates standard probe diameters up to 12 mm and supports simultaneous calibration of up to seven sensors via its included 7-port stainless-steel bath cover. Its 24 L working volume ensures adequate immersion depth (>15× probe length) for primary standard thermometers per ISO/IEC 17025 Clause 6.5.2. The system meets DIN ISO 9001:2000 requirements for process-controlled calibration infrastructure and is routinely deployed in GLP and GMP-regulated settings. Optional DKD-accredited calibration certificates (5-point, traceable to PTB) and CNAS-recognized NIM (China National Institute of Metrology) reports are available upon request. All firmware and hardware designs comply with IEC 61000-6-2 (EMC immunity) and IEC 61010-1 (safety for laboratory equipment).

Software & Data Management

While fully functional in standalone mode, the FK31-SL supports bidirectional communication via RS232 for remote parameter configuration, real-time data logging, and event-triggered reporting. When connected to JULABO’s optional LabSoft software (Windows-based), users gain access to audit-trail-enabled session records—including timestamps, operator IDs, calibration points, deviation logs, and pass/fail status—fully compliant with FDA 21 CFR Part 11 requirements for electronic records and signatures. Data export formats include CSV, XML, and PDF reports with embedded digital signatures. Internal memory retains ≥1000 measurement cycles with timestamp and error-code tagging for post-hoc root-cause analysis.

Applications

• Primary and secondary calibration of RTDs, thermistors, liquid-in-glass thermometers, and digital handheld probes per ASTM E74-22 and ISO 17025 Annex C
• Validation of temperature sensors in pharmaceutical cleanrooms, bioreactor monitoring systems, and sterilization autoclaves
• Reference source for thermometer intercomparison studies in national metrology labs
• Stabilized thermal environment for material property testing (e.g., coefficient of thermal expansion, glass transition onset)
• Supporting uncertainty budgeting in accredited calibration certificates through documented repeatability, reproducibility, and drift characterization

FAQ

What is the minimum immersion depth required for accurate calibration?
Minimum immersion depth is 15× the probe diameter or 75 mm—whichever is greater—to minimize stem conduction error, per ISO 5725-2 guidelines.
Can the FK31-SL be used with silicone oil at 200 °C?
Yes—the bath is rated for continuous operation at +200 °C with high-flashpoint silicone oils (flash point >300 °C); ensure fluid level remains above the pump intake port.
Is DKD certification included by default?
No—DKD (Deutscher Kalibrierdienst) accreditation is an optional add-on service requiring separate quotation and lead time; certificates are issued by DKD-accredited laboratories only.
Does the unit support external Pt100 feedback for chamber temperature control?
Yes—an integrated Pt100 input channel allows direct connection of external reference sensors for cascade control applications.
How often does the system require maintenance?
The FK31-SL is designed for maintenance-free operation under normal laboratory conditions; annual verification of temperature uniformity and stability per ISO/IEC 17025 is recommended.