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Heat Pipe Furnaces

Isotech metrology furnaces have more than 35 years of proven use and are widely used by the worlds’ leading NMIs. For the optimal use of fixed point cells the temperature uniformity should be less than 10mK over the length of the fixed point sample CCT/2000-13, “Optimal Realization of the Defining Points of the ITS-90…”

Isotech heat pipe furnaces offer essentially gradient free operation; heat pipes provide the ideal conditions for the creation and maintenance of ITS-90 fixed point cells. Unlike some other companies Isotech can provide heat pipe furnaces to suit Indium, Tin, Zinc, Aluminum, Silver and Copper fixed points.

Plateau length is determined by the difference in temperature between the heat pipe and cell – this can be adjusted to give a plateau of any length of up to tens of hours. Our controllers offer extra resolution and allow adjustment to 0.1°C right up to 1090°C. The Potassium and Sodium models have a cooling coil in the lid with connections to circulate tap water to keep the furnace lid cool protecting the SPRT and reducing heat load into the lab. A pre warming tube with a temperature approximately equal to that of the heat pipe made of a unique and gas-tight material, is provided to heat the SPRT prior to it being placed in a cell. The furnaces feature an adjustable independent and adjustable over temperature device to protect expensive cells and SPRTs as well as a second internal over temperature safety device.

Dual Furnaces

In addition to the heat pipe furnaces described the Dual Furnaces incorporate a second furnace which, because of its unique design, will safely (and without contamination) pre and post-condition the thermometers. There is also a separate storage enclosure for up to four thermometers with adequate support for the thermometer head.

With the Dual Furnace the thermometers are removed from their storage enclosure and placed in the pre-conditioning furnace. The furnace is slowly heated to the Cell temperature. The thermometers are protected from contamination by a slow air flux around them. One by one the thermometers are transferred into the cell for 20 to 30 minutes for calibration and thence back to the conditioning furnace. When all the thermometers have been calibrated, the conditioning furnace is slowly cooled back to 400°C whence the thermometers can safely be removed into room temperature.

New Features

From our own ongoing experience and customer feedback we have updated the Isotech Furnace Range to deliver the same proven performance and advanced features but with a number of convenience upgrades to make your life easier.

The controllers have now been relocated to the top for easier operation, we now include an SPRT Stand and Cable Tidies to keep your standards safe and Accessory Pods to keep the
furnace tops free from clutter. Our furnaces are programmable to automatically melt and freeze cells and feature both USB and Ethernet interfaces with bright crystal clear displays.


Technical Feature Value
Uncertainty <1mK (with cells)
Uniformity <10mK over length of fixed point sample
Control 0.1°C resolution
Communications Included as standard
PC Interface Included as standard
Resolution 0.1 (over whole range)
Core Size 52 x 432mm
Dimensions Height – 960mm, Width 600mm, Depth 690mm, Weight dual 119kg, heatpipe 115kg.


Dual and Heat Pipe Furnaces

125°C to 1090°C

Isotech metrology furnaces have more than 35 years of proven use and are widely used by the worlds’ leading NMIs. Our controllers offer extra resolution and allow adjustment to 0.1°C right up to 1090°C. The furnaces have been updated with additional features to make operation simpler and safer. Models 17702, 17705, 17705, and 17707.

  • Essentially Gradient Free
  • Heat pipe Operation from Indium to Copper
  • Simple Use - no zone offsets to adjust

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