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PRECISION
RESISTANCE THERMOMETRY |
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High Precision Platinum Resistance Thermometer
Type 5187SA
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5187SA High
Precision Platinum Thermometer.
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This four terminal thermometer is
designed to realize, with the highest
accuracy, the International
Temperature
Scale ITS-90 over the range -189°C
to 66O°C.
The design is the result of many
years practical experience and cooperation with the
National Physical
Laboratory, Teddington
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Construction
The resistance element is of pure platinum coiled and mounted in a
strain free construction.
The former is of fused silica and great care
is taken to ensure freedom from contamination.
All the joints are welded, the four leads from the element to the seal in the thermometer
head are heavier gauge platinum thereby avoiding the generation of
thermal e.m.f.'s at the junction with the element. The leads are brought
through a hermetic seal at the head of the thermometer and joined via
low loss terminals to copper flex in a specially constructed cable with
four conductors.
The cable is made with PTFE insulation to ensure low
dielectric loss so that the thermometer may be used with either d.c. or
a.c. measuring systems. The terminations are gold plated copper spade
tags. The thermometer tube is specially treated to avoid radiation loss
by the piping effect in its walls.
Each thermometer is supplied with a
purpose-made carrying case.
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Stainless
Steel Sheath
To reduce the possibility of damage the Type 5187SA thermometer may
be supplied with a protective stainless steel sheath, outside diameter
8-9mm, fitted into the thermometer head by means of three screws. The
thermometer is calibrated without the sheath and when this is in
position the response time is increased to about 20 seconds
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Specifications
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| Temperature Range: -189°C
to 660°C |
Calibration: Suitable for
calibration to ITS-90 up to max temp 660.323°C (F.P. Aluminum) |
Resistance at 0°C
(Rtp):
25 Ohms +/- 0.5Ohm |
R(Ga)/R(tp): Ratio not
less than 1.11807
R(Me)/R(tp): Ratio not greater than 0.844235 |
| Reproducibility: +/-0.001°C |
Gas Filling: Dry air
at 1/3 atmosphere |
| Basic Accuracy:
+/-0.001°C |
Dimensions:
Sheath - diameter 6.5 to 7.5 length 480 mm
Head - diameter 23 mm length 60 mm
Overall length: 540 mm
Immersion depth: 300mm |
| Self heating: 0.002°C
to 0.003°C with 1mA and the
thermometer bulb immersed in unstirred water |
Leads: Supplied with 4
meters of PTFE insulated cable fitted with gold plated copper
spade tags. |
| Case Size: 67 x 16 x 7 cm |
Net Weight: Including
thermometer 1.15kg |
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Calibration
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| CALIBRATION
OF PLATINUM RESISTANCE THERMOMETERS TO INTERNATIONAL TEMPERATURE
SCALE (ITS-90) |
| The table
below sets out the types of calibration available from NPL and their
uncertainties |
| Point |
Temperature°C |
Uncertainty
°C |
| Range 1 |
Range 2 |
Range 3 |
Range4 |
| TP argon |
-189.3442 |
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0.002 |
0.002 |
0.002 |
| TP mercury |
-38.8344 |
0.0005 |
0.0005 |
0.001 |
0.002 |
| TP water |
0.01 |
0.0005 |
0.0005 |
0.001 |
0.002 |
| MP Gallium |
29.7646 |
0.0005 |
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| FP indium |
156.5985 |
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0.001 |
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| FP tin |
231.928 |
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0.001 |
0.001 |
0.002 |
| FP zinc |
419.527 |
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0.001 |
0.002 |
| FP aluminum |
660.323 |
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0.004 |
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The Type 5187SA Platinum Resistance Thermometer maximum calibration will
be 660.232°C.
Note: TP - Triple point, MP -Melting point, FP - Freezing
point.
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