The Isotech 915 is, without doubt, the finest stirred liquid parallel ube calibration bath available. Uncertainties of less than 1mK can be obtained using best practice ratio methods. The bath can also be used to achieve ITS-90 Fixed Point Cells (Mercury to Tin Points) with absolute uncertainties below 1mK.

The Isotech Parallel Tube calibration bath is a development of the previous 815 model. It has many features that improve performance and ease of operation. It is suitable for the calibration of liquid in glass thermometers, industrial platinum resistance thermometers and standard platinum resistance thermometers. The Isotech 915 is also suitable for thermocouples and industrial temperature sensors and can also be used with Fixed Point Cells.


The temperature range of a standard Isotech 915 liquid calibration bath (915H) is 40°C to 300°C. Together with an external chiller, the Isotech 915 Parallel Tube Calibration Bath can extend the temperature limit to -65°C. The 915 has a wide temperature range using silicone oil and other suitable fluids. All components that come in contact with the fluid are made of stainless steel and are insulated with materials that are completely safe to use. The 915 used in combination with a chiller, uses the latest ozone-friendly gases.


The liquids circulate through a propeller that mixes the liquid and pushes through a specially designed opening in the back of the two parallel tubes. A variable speed motor optimises the flow as the viscosity of the fluid changes. Beneath the orifice, the fluid circulates over a mineral insulated heater and temperature sensors that regulate the temperature of the bath. The fluid flows upwards over the calibration tube and weirs over the tube. Then it goes into a collection container where it returns to the rear tube for recirculation. An angled side entry tube allows cooling by placing a cooling probe at the back of the two parallel tubes.


The standard temperature controller has a resolution of 0.01°C to 0.1°C, which is suitable for the four-digit display (all digits can be read with the Cal NotePad software). The standard regulator is  replacedable by a model with a display resolution of 0.01°C over the entire range. This High Stability controller (option 915/E) also offers better short-term temperature stability, see table. Due to the high cost of some silicone oils, the 915 with its seven litre capacity is relatively inexpensive to fill compared to many other baths. Changing the fluid is easily possible by using the built-in drain. The design also allows the expansion of liquids when raised to a certain calibration temperature.

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