Thermocouples & Thermoresistances0 pages
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nnnnOTFIL
nnnnThermocouples & Thermoresistances
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nnnnThermocouples
nnnnTemperature probes are basically two wires with particular thermoelectric features, electrically insulated from each
nnnnother and from the external protection body. This type of temperature gauge is very reliable and quickly responding.
nnnnDepending on their various construction features, they are individually optimized to fully fit in a great number of
nnnnindustrial applications. The most significant input data needed to design a temperature probe are operative
nnnntemperature range and working conditions.
nnnnMgO Insulation Thermocouples
nnnnMgO-insulated thermocouples are made of two or more wires, inside a highly compacted MgO insulation powder.
nnnnVarious materials can be used for the external metallic body, according to the specific working conditions. MgO-
nnnninsulated thermocouples are manufactured and tested according to ASTM E608, and comply to ANSI MC 96.1 or
nnnnDIN 43710 standards.
nnnnConventional Insulation Thermocouples
nnnnThe thermocouple leads are inserted in ceramic insulators, that are housed, together with alumina powder, in
nnnnprotective bodies to ANSI/DIN specifications. The main application of these temperature gauges is when no
nnnnvibrations, mechanical stresses or pressure loads are applied.
nnnnThermocouple Junction Types
nnnnThere are 3 types of wire junction in thermocouples. The type shall be chosen according to the characteristics of the
nnnnapplication. The below comparison chart might help.
nnnnE G U
nnnn<i=- l i I
nnnnSymbol | Type | Response Time | In Corrosive Environments | With Vibrations | Other Features |
E | EXPOSED JUNCTION | Very short | Not good | Not good | Shall be handled carefully to avoid damage to the junction. |
G | GROUNDED JUNCTION | Short | Good | Not good | Very good with high pressures (up to 3500 Kg/cm2, or 350 MPa). |
U | UNGROUNDED JUNCTION | Longer | Very good | Very good | Very good whenever parasitic emf could affect accurate measurement. |
Thermocouples, PDF-TCR-011-E-1/10
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