The most accurately defined temperatures are those defining points (fixed points) of ITS-90. The leading Primary Laboratories use large fixed point cells in deep calibration furnaces that utilise heat pipes to eliminate temperature gradients. This combination of cell and furnace gives the smallest of uncertainties. In the patented Isothermal Towers the fixed point cell and heat pipe (or heat siphon) have been combined to produce the ideal realisations for calibrating standard thermometers. Thermometers can only be calibrated accurately if they are immersed sufficiently. In Isothermal Towers a heated block (Immersion Compensator, patent applied for) sits on top the heat siphon/cell to fully compensate for the immersion characteristics of the unit under test. The Isothermal Towers performance has been fully evaluated against the most detailed and demanding requirements ever written: CCT/2000-13. All Isothermal Towers; Indium, Tin, Zinc and Aluminium meet all the requirements of CCT/2000-13 allowing laboratories to realise the smallest uncertainties, at a fraction of the cost of conventional Metrology Furnaces with Primary Standard Cells. Introducing the ISOTOwers You can purchase three Isothermal Towers; Tin, Zinc and Aluminium for a similar price as one conventional cell and heat pipe apparatus Isothermal Towers are simple to use, and very robust. Operation is risk free, as a combined apparatus there is no need to handle a fragile cell. No need for specialist training courses. Isothermal Towers remove the mystery from fixed point calibration. Easily set to provide a melt or freeze of 24 hours or more, lending themselves for automatic calibration and providing your lab with an all day long plateau....

Isotech Ultra Pure-Metal Freezing Point Cells are designed specifically to realize the liquid-solid equilibrium temperatures of certain high-purity metal elements, for calibration of thermometers at the ITS-90 Fixed Points. When you purchase an Isotech Sealed Freeze Cell you are not just purchasing a kilo of metal inside a graphite crucible sealed within a quartz shell, you are getting the fruits of more than 35 years of experience and learning of not only how to make such an artefact without introducing contamination but an Internationally accepted embodiment of an ITS-90 fixed point. The Isotech cells have been further developed and refined from cells designed and manufactured by Henry Sostmann, with the first international inter comparison results being published in 1972. In 2007 we combined 17 years experience of producing the best Metal Clad Slim Cells, with our experience of producing the most accurate Fixed Points sealed in quartz glass; to introduce Metal Clad Optimal Cells for the Primary Laboratory. These cells can be readily shipped between labs for intercomparisons, overcoming the difficulty of transporting Quartz Cells due to the increased airport security restrictions. Isotech’s accredited laboratory has the smallest uncertainties and can issue UKAS certificates with uncertainties as low as ±0.07mK at 0.01°C to ±2mK at 961.78°C, k=2....

The Water Triple Point is the most important fixed point, the only point common to the ITS-90 and the Thermodynamic Temperature Scale. It is an essential reference point for every temperature laboratory. The Jarrett-Isotech cells are the best standard, all cells are not the same, accept no inferior device. Total Confidence – The Internationally Proven Cells The Jarrett-Isotech cells have been in production since 1958. An independent comparison* in 1981 showed the first cell to be within 0.000006°C of the reference cell. The most recent international study organized by BIPM** consistently shows labs using both recent and older Jarrett-Isotech cells tightly grouped, tens of μK around the BIPM reference value. International comparisons prove the quality of the Jarrett-Isotech Cells and are unique in the number, and history of comprehensive evaluations. *“ Reproducibility of Some Triple Point of Water Cells” By George T. Furukawa and William R. Bigge. Temperature – Its Measurement & Control in Science & Industry Vol. 5 1982. ** Final Report on CCT-K7: Key comparison of water triple point cells. M Stock et al 2006 Metrologia 43 03001...

The Isotech Mercury Cell Model is constructed in a rugged, sealed stainless steel enclosure allowing the triple point of -38.8344°C to be realized both easily and safely. Total Confidence The embodiment of the Mercury Triple Point Cell was originally developed in the US with a very close cooperation between Henry Sostmann and Dr. Furukawa of N. B. S. (now NIST) over twenty years ago. The physical size, materials and metal purity are identical to this original design. The Mercury is distilled four times leaving impurities of 10 to 15 parts per billion. The cells made by Isotech still use the original design, purity and supplier of Mercury. In international intercomparisons the cells made by Isotech have always been within the National Laboratories uncertainty of calibration and with over 20 years of successful use throughout the world the cell embodies the finest traditions of production and use. After more than 20 years Dr. Furukawa opened some of the original cells and the Mercury was still above 99.99995% pure. A reflection of the long term performance of the design....

The Isotech Argon Triple Point Apparatus is a robust, simple to use and affordable solution for the realisation of the argon triple point. Many laboratories use liquid nitrogen comparators which are convenient and can be low cost but the nitrogen boiling point is not on the ITS-90. More seriously the LN point is below that of Argon. Many standard platinum resistance thermometers (SPRTs) are filled with a mixture of argon and oxygen and at -195°C will be under a partial vacuum which affects the self-heating of the SPRT leading to a larger calibration uncertainty. For many laboratories the high cost and complexity of previously available argon systems has been a barrier. Now after years of research Isotech have introduced a new system that is more affordable, simple to use and will allow more laboratories the benefits of being able realise the argon triple point. The Isotech system requires no electricity; the only consumable is liquid nitrogen – the 6N Pure argon is contained in a pressure vessel. A filling tube allows liquid nitrogen to initially cool this volume to approximately -195°C. Weights are then added to a pressure release valve to increase the nitrogen’s boiling temperature to just above the argon cells triple point. The argon settles into its triple point for around four hours, allowing an SPRT inside the re-entrant tube to be calibrated. At the argon T.P. to an accuracy of ±0.5 mK,k = 2...

Isotech Nitrogen Boiling Point Apparatus is designed specifically to realise and maintain the liquid/vapour equilibrium (boiling point) of nitrogen or argon, for the calibration of thermometers on the International Temperature Scale of 1990. The Boiling Point Apparatus is self-contained and refrigerated by liquid nitrogen or liquid argon, which must be supplied by the user. Either liquid is suitable for the purpose. Liquid nitrogen is generally less costly and more readily available than liquid argon. The Apparatus does not require electrical power for its operation. The Boiling Point Apparatus will maintain the liquid-vapour equilibrium of nitrogen (-195.798°C) or of argon (-185.8468°C) indefinitely, provided boiled-off gas is replenished. ITS-90 specifies the triple point of argon (-189.3442°C) as the low end of the long-stem Standard Platinum Resistance Thermometer range. As a practical matter, realisation of this triple point is a costly (in equipment and time) and complicated process. Most laboratories will choose to calibrate this end of the platinum range by comparison of the thermometer under test with a thermometer of known calibration. National Laboratories themselves will invariably calibrate thermometers submitted to them by comparison, realising the actual argon triple point only infrequently for calibration of their own reference thermometers. The National Physical Laboratory of England makes this statement: “Most thermometers (submitted for calibration) will involve measurements (by) … comparison with NPL standards in a bath of liquid nitrogen (about -196°C)” Model 18205 Comparator is designed for precisely such comparison calibration. It comprises a stainless steel dewar, an inner equalising block having wells for 3 thermometers, top connections for filling and monitoring the level of liquid coolant, a pressure safety blow-off and a manifold which may be used to thermally tie the thermometers under test to the equalising block with helium gas (option...

Model 426 is for Aluminium, Silver, Gold or Copper slim fixed point cells as well as for comparison calibration. Heat pipes provide the ideal conditions for the creation and maintenance of slim ITS-90 cells. The furnace core is a specially-designed stress-free isothermal heat pipe, which provides a very low thermal gradient along the core working length. The heat pipe is designed so that the inner wall is not subject to thermal expansion stresses from the outer wall before the heat pipe reaches conduction temperature. The working fluid is permanently and safely sealed within the plasma-arc welded enclosure. The Oberon can be used with Blackbody Fixed Point Cells....

The multi-functions of the Oceanus-6 is a unique concept from Isotech, so unique that it is currently the subject of a patent application. The Oceanus-6 is a complete calibration laboratory working over the temperature range 45°C below ambient temperature to +140°C. It permits the calibration of temperature sensors absolutely (at fixed points of the ITS-90 scale) or by comparison to a reference standard. It will calibrate both contact and non-contact thermometers such as optical pyrometers, surface sensors, liquid in glass thermometers as well as thermistors, thermocouples and resistance thermometers, whether they are short, long or odd shaped. Further it permits maintenance of reference standards by confirming the Ice or Water triple point at regular intervals. The Oceanus-6 has a calibration volume of 52mm diameter and 300mm deep and is supplied with the very latest technology digital indicator, timer and controller making the Oceanus-6 a complete self-contained calibration laboratory. The Oceanus-6 offers unprecedented accuracies of ±0.0002°C (2 Sigma) at the Water triple point and the Gallium melt temperature of 29.7646°C and up to ±0.005°C in the stirred liquid bath option (by comparison)....

This model is a lower cost alternative to the ITL M 18205. This model is a simple apparatus open to the atmosphere comprising a stainless steel dewar flask filled with liquid Nitrogen, an insulating layer which houses a metallic equalising block and thermometer holder. Lastly a split insulated lid reduces evaporation and permits easy addition of liquid Nitrogen. From time to time extra liquid Nitrogen must be added, approximately every 30 minutes, to keep the dewar flask full. The dewar flask is 100mm inside diameter and 280mm deep. The standard equalizing block houses four SPRTs or industrial thermometers up to 8mm in diameter, giving ±0.002°C temperature uniformity. Method of Operation A standard calibrated SPRT is placed in the equalizing block together with the sensors to be calibrated. The whole is allowed equilibriate. The level is checked and Nitrogen added as necessary and readings taken 10 minutes afterwards. The Isotech Simple Liquid Nitrogen Apparatus is safe to use, having no glass dewar flask internally to explode. A comprehensive handbook accompanies the apparatus which includes an article by Henry E. Sostmann on the corrections required to convert the calibration to the ITS-90 value of the Argon Triple Point....

Water The Isotech B8 30 130 Cell is small enough to fit into portable Dry Blocks such as the Venus and Europa models. For the larger blocks like the Oceanus Isotech recommend the B12 46 210 with its increased immersion depth. Gallium and Mercury Cells Like the B8 Cell the Slim Gallium Cell can be used in portable blocks like the Venus and Europa, or in stirred liquid baths. The Hydra and Orion have accessories available to support the cells. Indium to Copper Isotech’s Slim Cells have been in constant use since their introduction in 1990. The cells have always been made from the highest quality graphite and 6N (99.9999%) pure metals. After further investment in the lab, and gaining smaller uncertainties from UKAS, we reviewed and further refined our range of metal clad cells to give better accuracy and performance. The new professional ranges of cells have more metal inside providing an active immersion depth in the metal of 160mm. Metal Clad Isotech produced the first metal clad cells in 1990 and have much experience in the manufacture and calibration of high quality proven metal clad cells. Metal clad cells are recommended for all points from Indium to Aluminium. Quartz Clad These cells are recommended for Silver and Copper points, whilst available for the lower temperature points the metal clad versions are recommended as they are more robust, have the same performance and are more cost effective. Equipment for Slim Cells The Slim Cells can be used in the same apparatus as the larger cells, and the greater immersion depth will give the lowest uncertainties....

Isotech produces two eight way selector switches, one for resistance thermometers Model 954 and Model 958 for thermocouples. These switches have been designed for use in conjunction with our TTI range. The switches allow easy selection of connected sensors. They can be operated from either the front panel switch or from an RS232 interface that is provided as standard. Channel status is indicated via front panel LEDs. The Selector switches can be located adjacent to the sensors being calibrated, giving more flexibility than a permanently connected or stacked system. The PRT Switch has 4mm terminal posts that can accept bare wires or 4mm plugs. The thermocouple switch has eight miniature thermocouple connectors. These thermocouple connectors are thermally bonded to a platinum resistance thermometer that measures the temperature of the connector and hence the “cold junction”. The TTI range temperature indicators feature the ability to measure a remote cold junction and this permits a mixture of thermocouple types to be connected through the box. The I-Cal software supports Switchbox models 954 and 958 and, for automatic operation, two boxes can be connected together with a “master / slave” lead allowing them to be controlled from a single RS232 port and up to 16 sensors to be switched. The software can automatically switch between the boxes and connect the appropriate output to the TTI. This 16 channel operation is not convenient without the software and manual operation of two boxes together is not recommended....

The purpose of Cal NotePad (CNP) is to automatically log and display the temperature of an Isotech calibration bath together with the unit under test. Cal NotePad can be used with baths (or indicators) without PC interfaces by the user typing in values from the keyboard. The Cal NotePad can be used to identify the operator and the unit under test. With the click of a button data is logged with time information, it is also possible to log continually. The calibration bath temperature can be changed from the PC or from the calibration baths controller – Cal NotePad will display the temperature changes as they occur on the re-scalable chart display. For traceable calibration the unit under test should be compared to a calibrated standard thermometer. Cal NotePad can record the actual temperature of the bath from either the in-built indicator of an Isotech SITE model or from a variety of external instruments see list. If the external instrument has two channels (e.g. Isotech TTI) then the unit under test may be connected to channel B for logging with CNP. Alternatively the value can be typed in from the keyboard. Similarly the calibration bath controller value, actual temperature, SITE indicator value or unit under test value may also be entered manually. Then the manually entered data is combined with that gathered automatically and the resultant file can be opened in an external application such as Excel for the preparation of reports, certificates etc. Cal NotePad is designed for ease of use, it will give a chart of the system. When the operator determines the system is stable – easily seen from the chart then clicking a button will record time, operator, serial numbers of unit under test along with controller and indicator values. Cal NotePad can be used for semi-automatic calibration, see I-Cal Easy for a fully automated calibration solution....