Thermocouple reference thermostat

E cooling water coil F lower electric connection G vacuum/argon connection. This scheme shows the use of the furnace for thermal analysis experiments. L differential thermal analysis head H reference thermocouple joints I thermostatic water circulation J thermocouple wires ... 

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.)...

As was explained in the previous section, when an adsorbate contacts an adsorbent, heat is released. The thermal effect produced can be measured with the help of a thermocouple placed inside the adsorbent and referred at the room temperature (see Figure 6.3) [3,31,34,49], This is a version of the Tian-Calvet heat-flow calorimeter [50], This calorimetric technique is distinguished by the fact that the temperature difference between the tested adsorbent and a thermostat is measured. Consequently, in the Tian-Calvet heat-flow calorimeter, the thermal energy released in the adsorption cell is allowed to flow without restraint to the thermostat [3,31,34,49],... 

It is essential that any thermometers, thermocouples, thermistors, etc. used in the thermostat bath and equilibrium cell are accurately calibrated with reference to a standard thermometer. This point cannot be emphasized too strongly. 

As can be seen from their principle of operation (Figure 2.2), thermocouples are particularly suitable for the measurement of temperature differences, there being no need for a thermostat for the reference junction. Series connection into thermopiles, comprising up to 1000 thermocouples, permits the rapid measurement of temperature differences of 10 K, which is not achieved by other measuring techniques. Thus, thermocouples constitute ideal measuring instm-ments for the determination and continuous monitoring or control of minor differences of temperature. They are consequently used in many calorimeters. At temperatures above 1300 K, thermocouples surpass resistance thermometers for absolute temperature measurements because the precision of the latter instruments deteriorates rapidly in this range. The measurement uncertainty is on the order of 1% of the absolute temperature. 

Figure 11. Scheme of one of the microcalorimeters used for the simultaneous measurements of O2 consumption and heat production rates in perfused preparations. The thermal gradient layers (1) are made of semiconductor thermocouples mounted in series on each chamber. The preparation (2) is placed near the upstream extremity of one of the 8-cm long tantalum chambers, so that most of the heat it produces is transmitted to the surrounding aluminium block that functions as a heat sink. The four-way distributor, driven from outside the thermostatic jacket by a torsion bar and a pneumatic valve, directs the effluents of the preparation chamber and the control chamber to the drain, alternately via a jet in front of the O2 cathode (3) or directly (4) every 2 to 5 min. Immediately upstream of the calorimeter chambers, the downstream components of the heat exchangers (5) are wound together, in co-current, in close contact with an extension of the aluminium block (not represented on the drawing) (Reproduced from Reference [70] with permission). 

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