Reference disk thermocouple

Danley 2003,2004). In addition to the sample and reference sensors, an additional center thermocouple, denoted To (Tzero), is utilized for the heat flow measurements. Similar to the 910,2910, and 2920 modules, there are two raised platforms for the sample and the reference on a constantan disk, which acts as a heat leak. The sample and reference disk thermocouples are attached to the underside of each platform. Two AT measurements are made. The first is taken between the chromel wires that are attached to the chromel disk area detectors. In addition, ATo is measured between chromel wires attached to the sample chromel disk and the To sensor. A chromel wire is looped between the sample chromel disk and the Tq sensor, which measures the sample temperature at the raised pod. The Tq sensor temperature is measured at the junction of the constantan and chromel wires attached at the center of the heat leak base. 

Figure 3.3 Sonoelectrochemical cell used for electrosynthesis and voltammetric studies. 1, Sonic horn 2, transducer 3, to control unit of sonic horn 4, graphite counter electrode 5, argon inlet for degassing 6, Pyrex reservoir 7, platinum-disk macro- or microelectrode 8, copper cooling coil connected to the thermostatted water bath 9, titanium tip 10, platinum resistance thermocouple 11, SCE reference. (From Ref. 557, reproduced with permission.)...

These devices have a disk (e.g. constantan alloy) on which the sample and reference pans rest on symmetrically placed platforms. Thermocouple wire (e g. chromel alloy) Is welded to the underside of each platform. The chromel-constantan junctions make up the differential thermocouple junctions with the constantan disk acting as one leg of the thermocouple pair. 

Zirconia disk electrode. (1) Zirconia disk sintered to (2) platinum tube (3) alumina tube for insulating zirconia grit and platinum tube (4) zirconia grit (5) Pt,02 reference electrode (6) thermocouple (7) four-bore alumina tube ... 

The cell is based on a Du Pont differential scanning calorimeter cell. A view of the interior of the top of this DSC cell, showing the sample and reference platforms, is given in Fig. 4. The Du Pont DSC is a heat flow type DSC cell in which a constantan sheet ( thermo-electric disk ) that supports the sample and reference serves as the major heat flow path for transferring heat to the sample and reference pans and also as the common element of the differential thermocouple. This thermoelectric disk is mounted inside a silver heating block which has a silver lid. The sample and reference are in sealed metal pans so that the thermal environment is reproducible from run to run. 

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... 

In heat-flux DSC, the difference in heat flow into the sample and reference is measured while the sample temperature is changed at a constant rate. Both sample and reference are heated by a single heating unit. Heat flows into both the sample and reference material via an electrically heated constantan thermoelectric disk, as shown in Figure 31-12. Small aluminum sample and reference pans sit on raised platforms on the constantan disk." Heat is transferred through the disks and up into the material via the two pans. The dififerential heat flow to the sample and reference is monitored by Chromel-constantan area thermocouples formed by the junction between the constantan platform and Chromel disks attached to the underside of the platforms. The differential heat flow into the two pans is directly proportional to the difference in the outputs of the two thermocouple junctions. The sample temperature is estimated by the Chromel-alumel junction under the sample disk. 

Sample, constantan disk, reference, furnace, chromel disks, chromel-alumel thermocouples... 

Modules 910,2910, and2920 The TA Instruments Q series DSCs evolved from their 910,2910, and 2920 modules. The DSC 910,2910, and 2920 cells use a thermoelectric heat leak made of constantan (a copper/nickel alloy) as noted in Hg. 2.2. The sample and reference pans sit on raised platforms or pods with the constantan disk at their base. The temperature sensors are disk-shaped chromel/constantan area thermocouples and chromel/alumel thermocouples. The thermocouple disk sensors sit on the underside of each platform. The AT output from the sample and reference thermocouples is fed into an amplifier to increase their signal strength. The heating block is made of silver for good thermal conductivity and also provides some reflectivity for any emissive heat. 

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