Perkin-Elmer power compensation

Figure 2.5. Perkin-Elmer power compensation DSC open loop similar to the AT of a heat flux DSC and closed loop after adjusting from feedback to keep both DSC cells at approximately the same temperature [from Wunderlich (1990) reprinted with permission of B. Wunderlich and Elsevier].

Similar to the Mettler Toledo DSC, an advantage of the Perkin-Elmer power compensation DSC is the simplicity of its temperature calibration for any heating rate (Perkin-Elmer 1976). This was true for the sample holder of the Perkin-Ehner DSC-2, and it is true for the sample holder of the Diamond Pyris DSC, since the structure of the sample holder did not change. In general, the following equation describes the temperature calibration of a power compensation DSC on heating... 

In heat fiux DSCs on heating, the glass transition is observed as a jump in the baseline (i.e., heat flow signal) pointing downward, while in the Perkin-Elmer power compensation DSCs the glass transition is a jump in the baseline pointing upward, although lately a number of manufacturers have provided an option to select the direction of the endoterm-exotherm. 

The power compensation DSC instrument was first described by Watson et al.3) and by O Neill4) and it was developed into a commercial instrument by the Perkin-Elmer Corporation. It utilises separate sample and reference holders of low thermal mass, with individual heaters and platinum thermometers, as shown schematically in Fig. 1. In addidion to controlling the average temperature the instrument employs a... 

Fig. 1. Power Compensation DSC. Schematic Cross-Section of Perkin-Elmer DSC Cell. (Reproduces from Thermal Analysis Newsletter, Perkin-Elmer Corp., No. 9 (1970))...

This is one of the most frequently used methods to study solid-state properties. The flux t5q)e DSC involves heating the sample and reference samples at a constant rate using thermocouples, to determine how much heat is flowing into each sample and thus finding the differences between the two. Examples of such DSC instrumentation are those provided by Mettler and duPont. The power compensation DSC (e.g., Perkin-Elmer), an exothermic or endothermic event, occurs when a sample is heated, and the power added or subtracted to one or both of the furnaces... 

The DSC measurements reported in this book are performed with the power-compensating DSC-2 and DSC-7 systems from Perkin Elmer. The block surrounding the DSC sample holders is kept at -150°C + 1°C with the aid of a controlled liquid nitrogen supply, both cells are purged with helium (60 ml/minute). 

The major proof was that for the majority of materials the same calibration constant was found. Meanwhile, part of the AH values in Table 1 were confirmed by measurements with a Perkin-Elmer DSC-2, i.e. a power compensated calorimeter (Breuer, Eysel and Hohne ). 

A more recent step to speed up DSC was taken in connection with a commercial power-compensation DSC (High Performance DSC) [6] and is now available as HyperDSC from the Perkin-Elmer Inc. It is claimed to reach 500 K min. For a pan of a diameter of 5 mm, the heating rates calculated in Fig. A. 10.1 corresponds to sample masses of 20, 2, and 0.2 mg, showing that it is the heating and cooling capacity of the DSC that limits fast calorimetry, not the properties of the sample. 

A) Block diagram and (B) schematic diagram of power compensation DSC system (by permission of Perkin-Elmer Corp.)... 

DTA as well as power compensation DSC instruments, and is called temperature modulated DSC, or TMDSC. The following trade marks are used by different TA instrument manufacturers for their temperature modulated differential scanning calorimeters Modulated DSC (MDSC ) of TA Instruments Inc., Oscillating DSC (ODSC ) of Seiko Instruments Inc., Alternating DSC (ADSC ) of Mettler-Toledo Inc. and Dynamic DSC (DDSC ) of Perkin-Elmer Corp. 

Differential scanning calorimetry (DSC) is a method to determine phase transition temperamres and enthalpies [3]. In this thesis a power compensation DSC of the Perkin Elmer Corporation (DSC 8000) was used. 

Figure 23. Operating principle of a power-compensated differential scanning calorimeter (Perkin-Elmer)...

Two major types of DSC instruments are available on the market. The first one is the power compensation mode used in Perkin Elmer instruments. In this mode, sample and reference are kept at the same (changing) temperature and the power input that is needed to achieve this temperature is measured for both sample and reference. The second mode, which is used by the majority of DSC instrument providers, is called heat flux DSC. Here, the temperature difference between sample and reference is measured as a function of temperature, while both are heated or cooled in two compartments of one oven. The heat flow difference between sample and reference is then calculated from this temperature difference and the independently determined thermal resistance between sample and reference. Both methods yield essentially the same data ... 

One of these techniques that brought into science the name DSC, called today power compensation DSC, was created by Gray and O Neil at the Perkin-Elmer Corporation in 1963. The other technique grew out of differential thermal analysis (DTA), and is called heat flux DSC. Differential thermal analysis itself originates from the works of Le Chatelier (1887), Roberts-Austen (1899), and Kurnakov (1904) (see Wunderlich, 1990). It needs to be emphasized that both of these techniques give similar results, but of course, they both have their advantages and disadvantages. 

In addition to the description of the DSCs of the three best-known commercial manufacturers in the previous paragraphs, Netzsch, Setaram, Seiko Instruments, and Shimadzu are often encountered on the US market. These are all heat flux DSCs Perkin-Elmer is the only power compensation DSC manufacturer. 

Figure 2.40 shows an isothermal crystallization curve of a high-density polyethylene sample recorded by a Perkin-Elmer DSC7 (see Fig. 2.41 for Avrami plots). In the study of isothermal crystallization, the power compensation DSC is the preferred instrument among the presently available commercial DSCs, because the temperature difference between the sample and the reference cells is negligible, as described in Section 2.3. 

PerkinElmer Life and Analytical Sciences (PKI, Perkin-Elmer, Perkin-Ehner) offers two types of DSC modules. The first is constructed on a heat flux design, while the second design is based on the power compensation principle. Table 2.10 compares the characteristics of the two DSCs ... 

Two main types of commercial DSC instruments are in use, namely heat flux (hf) and power compensation (pc) instruments (c/r. ref. [21]). The power compensating version, originally developed by Perkin-Elmer Co. [56], employs two different ovens. DSC in the heat flux mode with one oven is similar in operation to a conventional... 

There are two basic methods in use in commercial instrumentation. Figure 7.2(a) shows the power-compensation method employed by Perkin-Elmer. It was this method which first attracted the name DSC , because the difference in power required to ramp the sample and the reference at the same rates is measured. In reality, of course, a difference in temperature between sample and reference is required to drive the differential power requirement. This highly elaborate method is then seen to suffer from many of the same problems as the technique originally suggested by Boersma [3] which uses a heat-flow disc to quantify the difference in the heat flow to sample and reference (Figure 7.2(b)). With proper engineering, this heat-flow difference is just proportional again to the temperature difference between sample and reference (AT). In... 

The first commercial DSC instrument was introduced by Watson and his co-workers at Perkin-Elmer (Model DSC-1) in 1964.1 1 Watson, et al., also appear to be the first to have used the nomenclature differential scanning calorimetry. Their instrument, a power-compensating DSC, maintained a zero temperature difference between the sample and the reference by supplying electrical energy (hence, the term power-compensation) either to the sample or to the reference, as the case may be, depending on whether the sample was heated or cooled at a linear rate. The amount of heat required to maintain the sample temperature and that of the... 

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