Cu-constantan

Unfortunately, the thermoelectric power vanishes when temperature tends to zero pairs as the classic Cu/constantan thermocouples show very low sensitivity below 10 K (see Fig. 9.2). 

Thermocouples, or thermal junctions, or thermoelectric thermometers have two intermetallic junctions between two different metals (or semimetals, or semiconductors) A, B in a loop (Fig. 10.21). When these two junctions are held at different temperatures (T i, and T2), then a potential difference A Vis set up this is the Seebeck98 effect. For instance, for a Cu-constantan thermocouple, with T2 = 300 K and T, 273.15 K, AV = 1.0715 mV. Its converse is the Peltier99 effect If a current at a fixed voltage is applied in a loop like in Fig. 10.21, then a temperature difference AT can be maintained (thermoelectric heaters and coolers). The Seebeck effect arises because, before the junctions are made, the two metals have different Fermi levels after the junctions are made, electrons will flow from the higher-level metal to the lower-level metal, until a single Fermi level results across the junction. 

Adams, Tables for Pt-Rh and Cu-Constantan couples. Jour, Am, Chem, Soc., 36 January, 1914. 

In the early days, thermocouples (Cu-constantan 15 tun) were used as detector. The Introduction of the OV-detector and the con-... 

Constantan, 45% Ni, 55% Cu, has high electrical resistivity and a very low temperature coefficient of resistivity. It is extensively used with copper as a thennocouple element. 

Type-T Thermocouples (Cu vs. Constantan). These are suited for measurements in the —200 to 350°C range they are often used for a differential measurement, since only copper wire touches the probes. Since both conductors are nonmagnetic, there is no Curie point and thus no abrupt change in characteristics. Type-T thermocouples have a sensitivity of about 43 gV/°C. 

Cupronickels contain from 15 to 20 per cent of nickel, the remainder being copper. They can be cold-worked for example they can be cold-rolled from I inch down to 0-05 inch without annealing being necessary. They have been extensively used for bullet jackets. The 2 5 Ni, 75 Cu alloy used in coinage has already been mentioned. A 30 Ni, 70 Cu alloy is used for condenser tubes. Another useful alloy, sometimes known as constantan, has 40 Ni and 60 Cu. Owing to its high electrical resistance and low resistance temperature coefficient it is used for standard electrical resistances. 

Cu and 40-55% Ni) that is recommended for a temperature range of 90-lOOOK and Copper - Constantan that is recommended for a temperature range of90-600K [243],... 

There are two main types of DSC instrumentation, heat-flux DSC and power-compensated DSC. A schematic of a commercial heat-flux DSC is presented in Figure 16.19. In a heat-flux instrument, the same furnace heats both the sample and the reference. In heat-flux DSC, the temperature is changed in a linear manner, while the differential heat flow into the sample and reference is measured. The sample and reference pans sit on the heated thermoelectric disk, made of a Cu/Ni alloy (constantan). The differential heat flow to the sample and reference is monitored by area thermocouples attached to the bottom of the sample and reference positions on the thermoelectric disk. The differential heat flow into the pans is directly proportional to the difference in the thermocouple signals. The sample temperature is measured by the alumel/chromel thermocouple under the sample position. This temperature is an estimated sample temperature because the thermocouple is not inserted into the sample itself. The accuracy of this temperature will depend on the TC of the sample and its container, the heating rate, and other factors. As shown in Figure 16.19, the sample and reference pans both have lids and the reference pan is an empty pan. A schematic of a power-compensated DSC is presented in Figure 16.20. The major difference in power-compensated DSC... 

For the medium-range tests of Au-Co vs. Ag-Au and constantan vs, Cu the wire goes directly from the first indicated temperature to the second for the other three pairs, an intermediate section of each wire is at room temperature. 

The insertion of the electroconductor wire as a sensing element (yam-based sensor) into a textile auxiliary wall was carried out during the weaving process. A number of thermocouples (type k constantan (Cn)/copper (Cu)) formed a thermopile, created with a posttreatment (Fig. 19.7(a)). This thermopile is judiciously disposed on both sides of the textile auxiliary wall to measure the temperature gradient (Fig. 19.7(b)). 

A wire of constantan (Omega Engineering, USA) with a diameter of 76 pm (p) was used as a monoconductor (MC) wire. Biconductor (BC) wire was prepared by an electrochemical deposition of copper (Cu), with a thickness of 10—20 pm, to the... 

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