| 1. |
- Bäckström, Gunnar, et al.
(författare)
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Determination of thermal conductivity tensor and heat capacity of insulating solids
- 1977
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Ingår i: Journal of Physics E: Scientific Instruments. - : Institute of Physics Publishing (IOPP). - 0022-3735. ; 10:8, s. 767-769
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Tidskriftsartikel (refereegranskat)abstract
- Specific heat capacity ρcp and thermal conductivity components λij for several classes of anisotropic crystals as well as isotropic materials may be determined by a transient method. The specimen is ground flat, the boundary plane being oriented parallel to two principal axes of the conductivity tensor. Two parallel metal strips in one of the principal directions are evaporated on to this surface. One is heated with a constant DC power, the other is used as an AC-driven resistance thermometer. It is shown that the temperature variation measured in response to a heat pulse permits λ and ρcp to be determined if the specimen is isotropic. If it is anisotropic, two parameters of the type λllλ33 and λll/ρc are obtained. Additional measurements with the strips deposited in the other principal directions enable λll, λ22, λ33 and ρcp to be calculated.
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| 2. |
- Bäckström, Gunnar
(författare)
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Determination of thermal properties using a shielded thermocouple
- 1982
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Ingår i: Journal of Physics E: Scientific Instruments. - : Institute of Physics Publishing (IOPP). - 0022-3735. ; 15:10, s. 1049-1053
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Tidskriftsartikel (refereegranskat)abstract
- A new version of the hot-wire method for measuring thermal conductivity is proposed. The sheath of a differential Thermocoax wire is heated by an electric current and the temperature is recorded before, during and after heating. An on-line desk computer fits the theoretical expression for the temperature to the data. Thermal conductivity as well as heat capacity for a fluid or plastic medium surrounding the wire may be determined.
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| 3. |
- Holm, Ulf, et al.
(författare)
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Measurement system for magneto-optic sensor materials
- 1984
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Ingår i: Journal of Physics E: Scientific Instruments. - : The Institute of Physics. - 0022-3735. ; 17:10, s. 885-889
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Tidskriftsartikel (refereegranskat)abstract
- A system for the measurements of magneto-optic properties of IR-transparent materials is described. The system is designed for the characterisation of fibre optic magnetic field sensor materials. Measurement results on YIG-crystals are prresented. The accuracy of Faraday rotation and light transmission measurements are ±2 mrad and ±2% respectively. Important features for the sensor characterisation are light beam scanning, temperature control and flexible magnetic field generation. A desktop computer is used for system control and data acquisition. The system is expected to be of great importance for future sensor developments.
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| 4. |
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| 5. |
- Sandberg, Olov, et al.
(författare)
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Heat capacity and thermal conductivity from pulsed wire probe measurements under pressure
- 1977
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Ingår i: Journal of Physics E: Scientific Instruments. - : Institute of Physics Publishing (IOPP). - 0022-3735. ; 10:5, s. 474-477
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Tidskriftsartikel (refereegranskat)abstract
- If a metal wire immersed in an electrically insulating medium is heated by a known constant power, the thermal conductivity of the medium may be deduced from the temperature variation of the wire. In this work it is shown that further analysis of this variation also permits the specific heat capacity or the thermal diffusivity to be determined. A nickel wire is used both as a heater and as a temperature sensor. The power is kept constant by electronic means, and the resistance measured by a four probe technique. Eight temperature values are recorded during the power pulse, which has a typical duration of 1 s. Data acquisition and calculation of thermal conductivity and specific heat capacity are carried out automatically using a desk calculator. This extended method has been tested by studying glycerol in its amorphous and crystalline states in the range 130-300 K and at pressures of up to 0.8 GPa.
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| 6. |
- Sundqvist, Bertil, et al.
(författare)
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Contactless resistivity measurements under high pressure
- 1983
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Ingår i: Journal of Physics E: Scientific Instruments. - Bristol : Institute of Physics. - 0022-3735. ; 16:5, s. 408-411
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, a contactless inductive method has been devised for measurements of the electrical conductivity of metallic materials under very high pressures (>1 GPa). A sample in the form of a thin disc is placed in a pick-up coil in a steady-state AC magnetic field. The output voltage from the coil is analysed with a lock-in amplifier to find the component due to eddy currents in the sample, from which the conductivity is calculated, using a semi-empirical expression. The influence of the steel pressure vessel is eliminated by making simultaneous measurements on a known reference material. Experimental results are shown for tin and sodium up to 1.3 GPa.
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| 7. |
- Sundqvist, Bertil
(författare)
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Low T hydrostatic limits of n-pentane/iso-pentane mixture measured by a self-supporting Manganin pressure gauge
- 1987
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Ingår i: Journal of Physics. E, Scientific Instruments. - Bristol : Institute of Physics. - 0022-3735. ; 20:8, s. 984-986
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Tidskriftsartikel (refereegranskat)abstract
- A simple design for a self-supporting Manganin pressure gauge is described. The shear-strain sensitivity of the gauge has been used to determine the hydrostatic pressure limit below 150 K of the 50/50 mixture by volume of n- and isopentane that is commonly used as a pressure-transmitting medium in high-pressure experiments.
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| 8. |
- Sundqvist, Bertil
(författare)
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Simple, wide range linear temperature-to-frequency converters using standard thermistors
- 1983
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Ingår i: Journal of Physics E: Scientific Instruments. - : Institute of Physics. - 0022-3735. ; 16:4, s. 261-264
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Tidskriftsartikel (refereegranskat)abstract
- The exponential voltage-time relationship of a charging RC circuit is used to linearise the approximately exponential resistance (R) against temperature (T) behaviour of a thermistor. The resulting output signal is a frequency, linear in and directly proportional to absolute temperature. Using standard, inexpensive thermistors a temperature error of less than 0.5K over a 75K range is obtained, the error being due to deviations from the thermistor's nominally exponential R(T) relationship. The circuit can be used to linearise any transducer having an exponential relationship between input and output signals, or to obtain an output signal proportional to the logarithm of any input voltage signal (that is, proportional to the input signal in dB).
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