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CALIBRATION SOLUTIONS
ITS-90 Isothermal Towers
156 to 660°C
ACROSS RAngE
g
High accuracy
g
Fast to temperature
g
Simple to use
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 Isothermal Towers the fixed point cell and heat pipe (or
heat siphon) have been combined (patent applied for) to
produce the ideal realisations for calibrating standard
thermometers.
Thermometers can only be calibrated accurately if they
are immersed sufficiently.
ISOTower
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
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.
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CALIBRATION SOLUTIONS
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Perfect Audit Item
Ceramic Ins ulators
Reflectors
Air
Q+
Q -
Q+
Q -
Q
FP
Cell
Conventional
New
Integrated Device
Immersion
Compensator
Isothermal
Zone, T1
Cell, T1
Heat Siphon
3 Hours
6.5mK
30 Hour Freeze / 50% 0.3mK
23 Hour Melt / 80% 1mK
2 Hours
3mK
As an audit item, an accreditation authority can send the
device to laboratories for intercomparison.
Because the cell, apparatus and immersion compensator
are a single entity, the performance is unambiguous unlike
existing systems where cell and apparatus are often
separated during intercomparison. Accreditation
authorities love them.
Available to Hire
Additionally Isothermal Towers are available to hire from
Isotech and a growing number of Isotech Distributors to
allow laboratories to audit themselves by intercomparing
their cells and standard thermometers to a UKAS
calibrated Isothermal Tower.
Transportable
ITS-90 Isothermal Towers are transportable by carrier;
there are no fragile glass parts!
n Isothermal Towers include a traceable calibration certificate.
This includes a graph of one freeze, one melt plateau and a
certificate of purity for the metal inside the siphonic cell.
As an option, UKAS calibration is available to one of two
services, see table over for the uncertainties.
Full data available at www.isotech.co.uk/isotower
A fixed point cell is not long enough to eliminate heat
conductance along the thermometer calibrated in it. Currently,
using long furnaces, heat shunts and reflective baffles an
attempt is made to reduce these losses.
The ISOTower uses a combined metal clad fixed point cell and
heat siphon, which when heated provides an isothermal
environment for the metal within to change state. The outer
wall of the cell becomes the inner wall of the heat siphon with
cost as well as performance benefits.
Additionally an Immersion Compensator is used to
compensate for the stem conduction problems caused when a
thermometer under test is not sufficiently immersed into a fixed
point cell.
Benefits of the ISOTower over a conventional
Quartz Cell and Apparatus
ISOTower
n Robust - no glass parts
n Easily Transported
n Integrated Device - known immersion characteristics
n Uniquely integrated cell, apparatus and correction for
thermometer stem conduction
n Simple and safe to use with increased confidence in
results
Conventional Quartz Cell and Apparatus
n Fragile and Risk of Breakage
n Difficult and expensive to Transport
n Cell certified separate from apparatus, stem conduction
unknown
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CALIBRATION SOLUTIONS
Specification
Model 490 491 492 493
ITS-90 Point Indium Tin Zinc Aluminium
Temperature 156.5985°C 231.928°C 419.527°C 660.323°C
Metal Purity 6N 6N 6N 6N
Plateau Duration Up to 30 hrs
UKAS Uncertainty: Premium Service* ±0.7mK ±0.8mK ±1mK ±2mK
UKAS Uncertainty: Standard Service* ±2mK ±2mK ±2mK ±6mK
Heating Time 2 hrs 2 hrs 2 hrs 2 hrs
Pocket Diameter 8 mm
Total Immersion Depth 290 mm
Depth of metal surface to bottom of reentrant tube 180 mm
PC Interface Supplied with PC Cable and Software
Power 900 Watts
Voltage 110 Vac or 230 Vac 50/60Hz
Dimensions H 430 mm x W 310 mm x D 300 mm
Weight 15kg
* UKAS Calibration is Optional, Uncertainties apply to whole system
n Immersion Compensator*
Fully compensates for the
immersion characteristics of the
thermometer under test.
n Siphonic Cell*
A combined Fixed Point Cell and
Heat Pipe
The outer wall of the fixed point cell
is the inner wall of the heat pipe or
siphon, thus integrating the cell and
its apparatus, giving a guaranteed
performance from the cell.
*Patent applied for
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