ISOTower Data Sheet - Isotech

156 to 660°CAcross rangeITS-90 Isothermal TowersISOTowerg High accuracyg Fast to temperatureg Simple to useThe most accurately defined temperatures are thosedefining points (fixed points) of ITS-90.The leading Primary Laboratories use large fixed pointcells in deep calibration furnaces that utilise Heat Pipesto eliminate temperature gradients. This combination ofcell and furnace gives the smallest of uncertainties.In Isothermal Towers the fixed point cell and heat pipe(or heat siphon) have been combined (patent appliedfor) to produce the ideal realisations for calibratingstandard thermometers.Thermometers can only be calibrated accurately if theyare immersed sufficiently.In Isothermal Towers a heated block (ImmersionCompensator, patent applied for) sits on top the heatsiphon/cell to fully compensate for the immersioncharacteristics of the unit under test.The Isothermal Towers performance has been fullyevaluated against the most detailed and demandingrequirements ever written: CCT/2000-13.All Isothermal Towers; Indium, Tin, Zinc and Aluminiummeet all the requirements of CCT/2000-13 allowinglaboratories to realise the smallest uncertainties, at afraction of the cost of conventional Metrology Furnaceswith Primary Standard CellsYou can purchase three Isothermal Towers; Tin, Zinc andAluminium for a similar price as one conventional celland heat pipe apparatus!Isothermal Towers are simple to use, and very robust.Operation is risk free, as a combined apparatus there isno need to handle a fragile cell. No need for specialisttraining courses. Isothermal Towers remove the mysteryfrom fixed point calibration.Easily set to provide a melt or freeze of 24 hours ormore, lending themselves for automatic calibration andproviding your lab with an all day long plateau.80 | SOLUTIONS FOR PRIMARY & SECONDARY LABORATORIES

Perfect Audit ItemAs an audit item, an accreditation authority can send thedevice to laboratories for intercomparison.Because the cell, apparatus and immersioncompensator are a single entity, the performance isunambiguous unlike existing systems where cell andapparatus are often separated during intercomparison.Accreditation authorities love them.Available to HireAdditionally Isothermal Towers are available to hire fromIsotech and a growing number of Isotech Distributors toallow laboratories to audit themselves by intercomparingtheir cells and standard thermometers to a UKAScalibrated Isothermal Tower.TransportableITS-90 Isothermal Towers are transportable by carrier;there are no fragile glass parts!ConventionalNewIntegrated Device23 Hour Melt / 80% 1mKCeramic InsulatorsReflectorsAirIsothermalZone, T1QFP2 HoursQ+Q -ImmersionCompensator3mKCell, T1CellHeat SiphonQ+Q -30 Hour Freeze / 50% 0.3mK3 Hours6.5mKA fixed point cell is not long enough to eliminate heatconductance along the thermometer calibrated in it.Currently, using long furnaces, heat shunts and reflectivebaffles an attempt is made to reduce these losses.• Isothermal Towers include a traceable calibration certificate.This includes a graph of one freeze, one melt plateau and acertificate of purity for the metal inside the siphonic cell.As an option, UKAS calibration is available to one of twoservices, see table over for the uncertainties.Full data available at www.isotech.co.uk/isotowerThe ISOTower uses a combined metal clad fixed point celland heat siphon, which when heated provides an isothermalenvironment for the metal within to change state. The outerwall of the cell becomes the inner wall of the heat siphon withcost as well as performance benefits.Additionally an Immersion Compensator is used tocompensate for the stem conduction problems caused whena thermometer under test is not sufficiently immersed into afixed point cell.Benefits of the ISOTower over a conventionalQuartz Cell and ApparatusISOTower• Robust - no glass parts• Easily Transported• Integrated Device - known immersion characteristics• Uniquely integrated cell, apparatus and correction forthermometer stem conduction• Simple and safe to use with increased confidence inresultsConventional Quartz Cell and Apparatus• Fragile and Risk of Breakage• Difficult and expensive to Transport• Cell certified separate from apparatus, stemconduction unknownSOLUTIONS FOR PRIMARY & SECONDARY LABORATORIES |81

SpecificationModel 490 491 492 493ITS-90 Point Indium Tin Zinc AluminiumTemperature 156.5985°C 231.928°C 419.527°C 660.323°CMetal Purity 6N 6N 6N 6NPlateau DurationUp to 30 hrsUKAS Uncertainty: Premium Service* ±0.7mK ±0.8mK ±1mK ±2mKUKAS Uncertainty: Standard Service* ±2mK ±2mK ±2mK ±6mKHeating Time 2 hrs 2 hrs 2 hrs 2 hrsPocket Diameter8 mmTotal Immersion Depth290 mmDepth of metal surface to bottom of reentrant tube180 mmPC InterfaceSupplied with PC Cable and SoftwarePower900 WattsVoltage110 Vac or 230 Vac 50/60HzDimensionsH 430 mm x W 310 mm x D 300 mmWeight15kg* UKAS Calibration is Optional, Uncertainties apply to whole system• Immersion Compensator*Fully compensates for theimmersion characteristics of thethermometer under test.• Siphonic Cell*A combined Fixed Point Cell andHeat PipeThe outer wall of the fixed point cellis the inner wall of the heat pipe orsiphon, thus integrating the cell andits apparatus, giving a guaranteedperformance from the cell.*Patent applied for82 | SOLUTIONS FOR PRIMARY & SECONDARY LABORATORIES