Isotech 798 Hydra Stirred Liquid Baths

The Isotech 798 Hydra series offers a versatile range of stirred liquid baths designed for precise and reliable temperature calibration across a wide span from –80 °C to 300 °C. With deep immersion, excellent uniformity and efficient fluid circulation, the Hydra provides performance that is rarely found in this price class.

Deep immersion that meets ITS‑90 recommendations

With an immersion depth of 300 mm, the Hydra meets the recommendations of the Supplementary Information to the ITS‑90, which calls for immersion depths of 15–20 cm between –50 °C and 50 °C, and 20–27 cm at 200 °C. Many baths in this category fall short, but the Hydra provides ample depth for long thermometers, SPRTs and industrial sensors.

Parallel Tube Action — superior uniformity

Instead of relying on simple stirring, the Hydra uses a parallel tube flow system. Fluid rises in the rear chamber and descends through the working volume, minimizing vertical and axial gradients. This produces a highly isothermal calibration zone and ensures low overall uncertainties.

Efficient design with low fluid volume

The calibration volume is 150 mm in diameter and 300 mm deep, yet requires only 5 litres of fluid. This reduces both initial and ongoing operating costs, especially when using specialty oils or alcohols. The circular design eliminates the cold corners often found in square tanks.

Advanced cooling and fast stabilization

The 798L and 798M models include built‑in refrigeration, while the 798H features an external cooling coil that can be connected to cold water or gas for faster cooldown. The Hydra cools from ambient to –80 °C in about 130 minutes, and heats from 25 °C to 200 °C in under an hour.

Thermal performance

The Hydra delivers excellent stability and uniformity:

• Absolute stability:
  • ±0.030 °C (ethanol, –80 °C)
  • ±0.017 °C (ethanol, –40 °C)
  • ±0.015 °C (oil, 250 °C)
• Vertical uniformity:
  • ±0.002 °C (oil, 50 °C)
  • ±0.005 °C (oil, 200 °C)

These characteristics make the Hydra suitable for high‑accuracy comparison calibration with SPRTs, PRTs and industrial sensors.

Ease of use and practical features

The Hydra benefits from Isotech’s long experience in liquid bath design. It drains quickly, is easy to operate and includes:

• > over‑temperature protection
• > commercial‑grade chillers (1/3 HP)
• > overflow and drain connections
• > compatibility with sensor supports and ITS‑90 fixed‑point cell holders

This combination of features makes the Hydra both robust and highly practical.

The Isotech 798 Hydra delivers deep immersion, excellent uniformity and strong thermal stability in a compact, cost‑effective package. With its parallel tube action, low fluid requirement and wide temperature range, the Hydra is an outstanding choice for laboratories seeking reliable and accurate temperature calibration.