Isotech 813 Stirred Ice Water Bath

The Isotech 813 Stirred Ice/Water Bath provides a highly stable and reproducible environment for calibrations at 0 °C, the most frequently used reference point in temperature metrology. While a simple ice‑water mixture in a Dewar is often used to achieve 0 °C, this method can introduce significant errors. Because water is densest at 4 °C, the temperature at the bottom of an unstirred Dewar can rise to that value, leading to deviations of several degrees. The 813 eliminates these issues by actively stirring the mixture and separating the ice from the measurement zone. The result is a uniform, stable and traceable 0 °C environment designed in accordance with national laboratory recommendations.

A stable 0 °C reference through active stirring

At the core of the 813 is a dedicated measurement compartment surrounded by ice. The water is continuously stirred to prevent temperature gradients, ensuring that the entire calibration zone remains at a true 0 °C. Up to four probes can be placed in the bath simultaneously.

Using demineralised water, accuracies of ±0.005 K are achievable. When comparison techniques are used — for example with an SPRT and a microK bridge — uncertainties can be reduced to ±0.001 °C.

Practical design for routine laboratory use

The bath has a capacity of approximately 8 litres and an immersion depth of 350 mm, making it suitable for long‑stem thermometers. A typical ice charge lasts around four hours before replenishment is needed. The 813 is compact, robust and easy to operate, with a low power requirement of just 50 W. It is ideal for laboratories that require a reliable and repeatable 0 °C reference.

Options and accessories

The 813 can be equipped with several useful accessories:

• > Copper Equalising Block (814/01b)
• > Mercury Thermometer Support Kit (814/02)
• > Small Water Triple Point Cell Kit (814‑06‑02)
• > Large Water Triple Point Cell Kit (814‑06‑04)

These options allow the bath to support both standard 0 °C calibrations and the maintenance of a Water Triple Point Cell.

The Isotech 813 Stirred Ice/Water Bath delivers a precise, stable and practical solution for 0 °C calibration. With its active stirring, deep immersion and excellent temperature uniformity, the 813 is an essential tool for laboratories requiring a dependable and traceable reference at the freezing point of water.