The Isotech Model 526 is a portable low temperature calibration source designed for both laboratory and field use. It provides controlled, stable temperature generation down to −115°C, supporting reliable calibration of sensors used in ultra-low freezers, pharmaceutical storage, and industrial processes.
Developed from Isotech’s long-standing expertise in temperature metrology, and building on the legacy of the Model 525, the Model 526 offers a practical solution for ultra-low temperature calibration.

Why Choose the Model 526?
Ultra-low temperature calibration presents specific challenges. Stability, uniformity, and control become increasingly difficult as temperatures fall below −80°C. The Model 526 has been designed to address these challenges while remaining practical for day-to-day use.

Key features:
• Temperature range from −115°C to 50°C
• Stability of ±0.03°C across the full operating range
• Free Piston Stirling Cooler (FPSC) technology for reliable deep cooling
• Controlled axial and radial temperature distribution
• 0.01°C resolution for precise adjustment and measurement
• Suitable for both laboratory and field calibration work

The Model 526 meets the requirements of EURAMET cg-13 for temperature block calibrators.

A range of accessories is available to support different calibration requirements and working environments:
• Carry case for transport and field use
• Alternative inserts including B and C types, and custom drilled to suit your probes
• I-Cal Easy software for automated calibration, data logging, and certificate generation

At ultra-low temperatures, performance must be both measurable and repeatable. The Model 526 provides a stable calibration environment suitable for verification and validation work.

• Consistent performance across the full temperature range
• Repeatable conditions for sensor calibration and comparison
• Suitable for use with external reference thermometers

When used as part of a complete system, accuracies of up to ±0.05°C can be achieved dependent on the reference thermometer and indicator , calibration status and insert configuration.

The Model 526 low temperature calibration source has been engineered for applications where reliability and usability are essential.

• Cooling from ambient to −115°C in approximately 90 minutes
• Heating from −115°C to 50°C in approximately 90 minutes
• Typical stabilisation time of 15 minutes
• Portable design (12kg) suitable for site and cleanroom use
• Environmental protection reduces moisture ingress and ice formation

The Model 526 uses inserts designed specifically for ultra-low temperature operation, improving both performance and usability.

• Optimised thermal mass and surface contact
• Reduced axial and radial temperature gradients

• 130 mm immersion pocket depth, 180 mm total well depth (including 50 mm insulating cap)

• Surface treatment to reduce probe sticking at low temperatures

Each unit is supplied with a standard multi-hole insert and insert removal tool.
Custom-drilled inserts are available to suit specific probe diameters.

The Model 526 can be used as a standalone instrument or integrated into a full calibration system.

Compatible with:

• Isotech reference thermometers
• Precision indicators
• I-Cal Easy software for automated calibration, data logging, and certificate generation

This allows straightforward progression from basic checks to fully traceable calibration.

The Model 526 is supported by Isotech, drawing on over 45 years of temperature calibration experience and backed by global technical support.

The Model 526 is suitable for a wide range of ultra-low temperature calibration tasks:

• Pharmaceutical cold chain validation (−70°C to −80°C storage)
• Medical and bio-banking applications
• Calibration of ultra-low freezers and environmental chambers
• Aerospace and environmental testing
• Food processing and flash-freezing systems
• Industrial and laboratory calibration below −80°C

Model 526 Data Sheet