The most used temperature for calibration is 0°C. The normal way of creating 0°C is via a mixture of ice and water in a Dewar Flask. However, this can give errors of up to 4°C because water is densest at 4°C and so as the ice melts the temperatures at the bottom of the flask can rise to 4°C. In the design of the ice flask offered by Isothermal Technology Ltd., these problems have been eliminated by stirring the water/ice mixture and segregating the ice from the water in the measuring zone. This stirred ice/water bath is designed and built according to National Laboratory recommendations. Using demineralised water, accuracies of ±0.005K are obtainable. Typically the bath will last for 4 hours before recharging with ice. The ice is contained around and below the compartment where up to 4 probes can be placed for calibration or referencing purposes. An option permits a water triple point cell to be maintained within the stirred ice bath....

The 670SQ is our latest thermometer, to be specifically designed to give optimum performance up to the aluminium point. Its construction permits the four internal platinum lead wires to expand and contract in the same manner as those of silver-point thermometers. The all-quartz construction of the support members gives the most stable performance with minimal drift, and a unique platinum radiation shield prevents heat radiating up the inside of the sheath. The construction, including the coiled sensing element, heat-shunt baffles and light scattering barriers, creates a thermometer of unsurpassed stability. Because the 670SQ goes beyond the temperature range of oxide growth to the level at which the oxide dissociates, the 670 is filled with a unique argon/oxygen mixture. A 2.5 metre length of low thermal EMF, high temperature, screened cable is connected in the handle, via a strain-relieving transition, to the all pure platinum construction of the thermometer. Gold-plated U-shaped terminals complete the cable construction, and the 670SQ is delivered in an elegant soft lined carry-case of our own design. A 670SQ is supplied only after a stabilising process which is complete when the reproducibility of RTPW is within 0.0005°C after excursions to the extremes of its temperature range. Values of RTPW and Wga are routinely provided with the 670SQ. The 670SQ can be supplied with RTPW and Wga only or with full UKAS calibration. “With calibration” means that you will get an Internationally accepted Fixed Point calibration. For best accuracy, recommended maximum measuring current for the 670SQ is 1mA for the 25.5Ω(Ro). A comprehensive handbook and tutorial will help you get the very best performance and stability from your 670SQ. The 670SQ 650mm long is our recommended SPRT offering ultra stability, vibration, shock, immersion and self heating characteristics. From the success of the original Model 670 SPRTs we have introduced new models into the 670 range offering metal she...

Isotech has produced over 200 high temperature thermometers which have been sold world-wide for use up to the silver point. As a consequence of our predelivery testing alone we have probably made more silver point calibrations than anyone else in the world. No one fully appreciates all the mechanisms at work when a coil of pure platinum wire inside a quartz envelope is taken to 1000°C and back. However, endless hours of study at National and International level, plus our own significant work at Isotech, have enabled us to design, build and test a superior Silver-Point Thermometer. This, we feel, is a significant contribution to better high temperature calibration. First, the 96178 can breathe, a valve in the handle can be opened to allow oxygen depletion or moist air to escape from inside the sheath and be replaced by fresh air containing 20% oxygen. The valve is normally opened at elevated temperatures and closed to prevent moisture ingress before water triple point measurements are performed. Second, the 96178 is the only thermometer ever designed with platinum heat radiation shields built into the sheath, to prevent heat radiating up inside the sheath. Third, a new ultra pure quartz, developed for the semiconductor industry at a cost of between 20 and 30 million pounds, has been adopted for use in the construction of the 96178. This new thermometer exemplifies our commitment to achieve the highest possible quality and minimum of contamination. How the thermometer is handled is most important for its stability and a purchaser will receive a comprehensive manual and tutorial with each 96178. Under some circumstances, provided the interior of the thermometer is undamaged we can replace the outer quartz sheath. Please consult us if a replacement is required. To exploit fully the accuracy of the 96178, a user will need a furnace for warming and annealing the thermometer as well as one to house the silver-point/aluminum-point cells. A Dual Calibration Furnace from Isot...

The ITS-90 specifies the SPRT to the freezing point of silver, 961.78°C. Thermocouples can be used beyond this temperature but it is difficult to see small changes in temperature. For a Type R thermocouple the voltage sensitivity at the copper point is 14μV/°C; a change of 1 μV is equivalent to a voltage change of 71mK. When using thermocouples electrical noise limits the ability to follow small changes in the copper freezing plateau and so attention was turned to the development of a new resistance thermometer allowing better measurements to be made. Isotech has a long history of making SPRTs to the Silver point (Model 96178) and this experience was combined with new research to produce the new copper point SPRT (Model 108462). Ro is nominally 0.25Ω the same as the silver point SPRT but the platinum winding is held in place on a new type of synthetic sapphire mandrel. The platinum ‘loves’ oxidising but ‘hates’ reducing atmospheres. The thermometer sheath is made of alumina. It is air filled and hence surrounded by 20% oxygen. Uniquely the sheath is connected to a small air pump to pressurise the 108462 with air so that any leakage is outwards, whilst maintaining an oxygen rich atmosphere around the winding. This is what gives the thermometer its stability. The four platinum lead wires are separated with tubes of quartz glass and passed through four bores. In use the winding is biased to +9V DC with the included ioniser....

This economically-priced Standard Platinum Resistance Thermometer, Model 909, is the workhorse of calibration laboratories all over the world. During 2007 we reviewed our range of SPRTs and now have new models in the 909 family, the 909L and 909H. The wide temperature ranges and economic pricing make this thermometer ideal for the secondary laboratory. For smaller uncertainties to suit the Primary Laboratory refer to the Model 670 SPRTs. The resistance element is of pure platinum, coiled and mounted in a strain free construction. The former is of pure alumina material and all parts have been pre-aged to eliminate contamination and strain. All joints are welded to minimize resistance changes. The leads are brought to a handle assembly where they are connected to a low loss cable, 2M long and screened. The 909Q has a quartz sheath while the 909L and 909H have metal sheaths. Whilst metal sheathed thermometers appear more robust than the quartz glass models it should be noted that ALL SPRTs are fragile devices and must be handled with care. Three thermometer lengths are available, standard length 480mm, extra length 550mm or maximum length 600mm. Quartz glass thermometers have the advantage that the internal components are visible and can be inspected and continue to be our recommended models. The low temperature models have excellent immersion characteristics and a significant cost saving when compared to the higher temperature models. The Model 909 is supplied with a calibration certificate giving RTPW and Wga. Alternatively we can provide a complete UKAS calibration certificate, see table opposite. For transportation and storage the Model 909 is supplied in its own attractive carrying case....

These industrial platinum resistance thermometers (IPRT / PRT) are ideal for field and lab use. Suitable for use as working standards in Dry Blocks and Liquid Baths or as high accuracy probes for our range of True Temperature Indicators. NEW: We now have 90 degree angled probes to a maximum temperature of 660°C. They are primarily for use in our Portable Temperature Calibrators for applications where the units under test have a terminal head fitted that would otherwise obstruct a longer reference thermometer. These sensors should be calibrated as part of the Portable Calibrator. All the thermometers are metal sheathed and both less fragile, and more affordable than the Isotech range of true Standard Platinum Resistance Thermometers that are used in laboratories and our found in our publication “Solutions for Primary and Secondary Laboratories”. All the thermometers use handmade Pt100 coil wound platinum sensing elements (RTD) to give high accuracy and low drift. Isotech’s UKAS accredited lab can calibrate to the smallest of uncertainties. Calibration should be specified to suit the particular operating range and application. Isotech can advise on which service is appropriate to match the temperature range and application....

Since 1995 Isotech have been producing various designs of special Au/Pt, Pt/Pd, Pd/Au thermocouples for researchers. From our experience we can now offer the most popular of these, the Pt/Au thermocouple in a standard form. All wires are 99.999+% pure and are fully annealed according to the recommendations of McLaren. Assembly also follows his prescriptions which have never been bettered. After final assembly and annealing the Pt/Au thermocouples will conform to IEC 62460, Edition 1 2008-07. For the smallest uncertainties we calibrate the thermocouple at the Zinc, Aluminium and Silver Fixed Points....

Probes are suitable for use with all Isotech thermocouple reference units or may be used with any other equipment including ice flasks and ice point reference units. They can be supplied to suit a single thermocouple, or up to ten double junctions in a single assembly. These probes are normally specified to order, or are made to match the reference equipment to which they will be fitted. Normal lead length, L2, is 1M but can be specified at the time of order along with the probe length, L1. All wire material is to the highest grade available and PTFE insulated, numbered and colour coded for the appropriate thermocouple type. Double junctions are most commonly supplied (four wire connections per junction). Single junctions (two wire connections per junction) can also be supplied. For Types R & S cold junctions are most commonly made from low cost compensating cable but can be supplied in platinum material to special order. Standard thermocouple Types are, K, E, J, T, N, U, S and R. Other materials available on request For Isotech reference units simply advise which model the junctions are for, and the types and number required. For custom junctions the following information is required....

These Platinum / Palladium Thermocouples (Pt/Pd) are manufactured by the National Physical Laboratory (NPL) who have developed a novel physical mechanism which mitigates the mechanical stresses caused by the different thermal expansion of Pt and Pd wires. This dispenses with the fragile coil conventionally used with this type of thermocouple. Platinum / Palladium thermocouples are more costly than Platinum / Platinum Rhodium types but benefit from superior performance, both in terms of stability (less de-calibration) and accuracy. Gold / Platinum Thermocouples (Au/Pt) offer the best performance but are limited to a maximum temperature of 1000°C. These Pt/Pd thermocouples offer lower drift than Platinum / Platinum Rhodium (Pt/Pt-Rh)and with higher operating temperatures than Au/Pt. They are suitable for a range of applications including transfer standards. In addition to developing the novel structural design along with new annealing and construction procedures NPL have established the world’s first ISO 17025 (UKAS) accredited calibration services using metal-carbon eutectic fixed point cells....

The Isothermal range of Thermocouple Standards are the result of many years development. The type R and S standards will cover the range from 0°C to 1600°C. The measuring assembly comprises a 7mm x 300mm or 600mm gas tight 99.7% recrystallized alumina sheath inside which is a 2.5mm diameter twin bore tube holding the thermocouple. The inner 2.5mm assembly is removable since some calibration laboratories will only accept fine bore tubed thermocouples and some applications require fine bore tubing. The covered noble metal thermocouple wire connects the measuring sheath to the reference sheath which is a 4.5mm x 250mm stainless steel sheath suitable for referencing in a 0°C reference system. Two thermo electrically free multi-strand copper wires (teflon coated) connect the thermocouple to the voltage measuring device. The thermocouple material is continuous from the hot or measuring junction to the cold, or referencing junction....

The Isothermal range of Thermocouple Standards are the result of many years development. The type R and S standards will cover the range from 0°C to 1600°C. The measuring assembly comprises a 7mm x 300mm or 600mm gas tight 99.7% recrystallised alumina sheath inside which is a 2.5mm diameter twin bore tube holding the thermocouple. The inner 2.5mm assembly is removable since some calibration laboratories will only accept fine bore tubed thermocouples and some applications require fine bore tubing. The covered noble metal thermocouple wire connects the measuring sheath to the reference sheath which is a 4.5mm x 250mm stainless steel sheath suitable for referencing in a 0°C reference system. Two thermo electrically free multistrand copper wires (teflon coated) connect the thermocouple to the voltage measuring device. The thermocouple material is continuous from the hot or measuring junction to the cold, or referencing junction....

These thermocouples are suitable for use as references in Isotech Dry Blocks and for use with temperature indicators. Details of our laboratory grade Standard Thermocouples with separate cold junctions can be found in our publication “Solutions for Primary and Secondary Laboratories”. These semi standards are lower cost and suitable for a variety of industrial applications. The 935-14-91 is constructed from Platinum and Platinum Rhodium alloys and can be used to 1300°C. Recommended for the Pegasus 1200 and general purpose applications. It has 1M of compensating cable terminated with a miniature thermocouple plug. The 935-14-88 is similar to the 14-91 but is made entirely from precious metals, with platinum wires all the way to the miniature plug. There are a range of high quality mineral insulated metal sheathed (MIMS) Type N thermocouples. These devices are lower cost than the noble metal types and can be bent to a desired shape if required. They are suitable for use in Isotech Dry Blocks and for general purpose measurement and calibration applications. The system accuracy or uncertainty will depend on the application and what instrument they are used with. The table shows the uncertainties that we can offer with optional UKAS calibration from our accredited laboratory....