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Nitrogen Boiling Point Aparatus
Isotech LN2 Nitrogen Boiling Point Apparatus

Product Code: ITL-M-18205
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Comparison Calibrator

Nitrogen Boiling Point Apparatus "LN2"

Boiling Point of Liquid Nitrogen
Gas Manifold for Thermometers
Self Contained - Bench Mounted

Isotech Nitrogen Boiling Point Apparatus is designed specifically to realize and maintain the liquid/vapour equilibrium (boiling point) of nitrogen or argon, for the calibration of thermometers on he International Temperature Scale of 1990,

The Boiling Point Apparatus is self-contained and refrigerated by liquid nitrogen or liquid argon, for the calibration of thermometers on the International Temperature Scale of 1990.

The boiling Point Apparatus will maintain the liquid-vapour equilibrium of nitrogen (-195.198°C) or of argon (-185.8468°C) indefinitely, provided boiled-off gas is replenished.

ITS-90 specifie 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, realization 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 measurement (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 equalizing block having wells for 3 thermometers, top connection 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 equalizing block with helium gas (optional).

Since the slopes (dR/dT) of Standard Platinum Resistance Thermometers are very similar at any temperature, calibration uncertainties not larger than 0.002K can be obtained at a small fraction of the cost of an absolute calibration.
Model ITL-M-18205
Temperature Range -185°C or -196 °C nominal
Uncertainty ±0.002°C

The temperature distribution across the copper block is less than 2mK. To this must be added the uncertainty issued with the calibration certificate from the National Laboratory.
Extra uncertainties will also exist if siddimilar probes are compared.
Power N/A
Dimensions Below flange 430mm
Diameter below flange 127mm
Flange diameter 165mm
Weight 14kgs

The nitrogen Point Apparatus may be adapted for use with liquid argon. Please contact the factory for details.

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