Copper resistance thermometer

For this cryostat a 150-ohm, No, 40 AWG copper resistance thermometer and the heater resistance wires are non-inductively wound in alternate, silicone-varnished, helically-machined grooves of the cylindrical copper vessel, 1, and then are varnished and baked, An uncoated, 1-watt, 56-ohm carbon composition resistor and a low temperature thermistor are sealed with epon resin and silk thread spacers into snug copper cylinders brazed to the top end-plate of 1. 

Copper resistance thermometer. Copper is an excellent material for resistance thermometers. Its availability in a pure state makes it easy to match with established standards. The resistivity curve of copper is a straiihf-line function of temperature between -60 and 400°F, and that makes copper resistance thermometers suitable for the measimement of temperature differences with high accuracy. Copper resistance thermometers are reliable and accurate means of temperature measurement at moderate temperature levels. 

FIG. 8-61 Typical resistance-thermometer curves for platinum, copper, and nickel wire, where Rj = resistance at temperature T and Rq = resistance at 0 C. 

Resistance thermometers are made of a pure metal, such as platinum, nickel, or copper. The electrical resistance of such a material is almost linearly dependent on temperature. Resistance thermometers are stable, having a small drift. A widely used and the best-known resistance probe is the IW-100 probe, which is platinum, having a resistance of 100 ohms at the temperature of 0 °C. Other resistance values for PT probes are available. The resistance versus temperature values as well as tolerances for platinum probes are standardized. The shape and size of a resistance probe can vary considerably, resulting in changes in probe dynamics. 

Fig. 7.18 (continued) (c) Light scattering apparatus used to detect polymer-polymer demixing 1 - HeNe laser, 2 - sapphire window, 3 - polymer film, 4 - photodiode array, 5 - copper block, 6 - resistance thermometer, 7 - temperature controlled jacket, (Reproduced with permission from Zywocinski, A., et al. J. Polymer Sci. Polym. Phys. 33, 595 (1995))... 

Some researchers, aware of the temperature problem, elect to use electrically heated wires for heat sources. The same wires can be used as resistance thermometers with satisfactory accuracy. A drawback, however, is that tests cannot be made in the transition region of boiling, because of instability. In addition, unless the wires are quite small the currents needed become very great. For example, if a -in.-diam. copper tube with a 0.03-in. wall is intended for use with water near the critical AT, a current of about 8,000 amp. is required. 

Very recently, Bailey and Richards (23) have shown that a high degree of sensitivity for adsorbed species can be achieved by measuring the absorption of infrared radiation on a thin sample cooled to liquid helium temperature. The optical arrangement used in these studies is shown in Figure 10. The modulated beam produced by the interferometer is introduced into the UHV sample chamber and reflected off a thin slice of monocrystalline alumina covered on one side by a 1000 k film of nickel or copper. Radiation absorbed by the sample is detected by a doped germanium resistance thermometer. The minimum absorbed power detected by this device when operated at liquid helium temperature is 5 x 10 14 W for a 1 Hz band width. With this sensitivity absorbtivities of 10"4 could be measured. 

RTDs are constructed of a resistive material with leads attached and placed into a protective sheath. Platinum resistance thermometers are the international standard for temperature measurements between the triple point of H2 at 13.81 K (24.86°R) and the freezing point of antimony at 630.75°C (1,167.35°F). The RTD elements include platinum, nickel of various purities, 70% nickel/30% iron (Balco), and copper, listed in order of decreasing temperature range. Their features and relative performance characteristics in comparison with other sensors are tabulated in Table 3.169. 

Here, the heat evolved on adsorption increases the temperature of the sample and its container (usually a copper cylinder). The heat is prevented from flowing to the peripheral shield (the surroundings ) by an appropriate control of the shield temperature. Thus, the shield is usually maintained at the same temperature as the sample container by the use of a differential thermocouple and a heat coil - as indicated in Figure 3.14. The temperature rise is measured by means of a resistance thermometer attached to the sample container. 

Experimental. A Parr model 1221 oxygen bomb calorimeter was modified for isothermal operation and to ensure solution of nitrogen oxides (2). The space between the water jacket and the case was filled with vermiculite (exploded mica) to improve insulation. A flexible 1000-watt heater (Cenco No. 16565-3) was bent in the form of a circle to fit just within the jacket about 1 cm. above the bottom. Heater ends were soldered through the orifices left by removing the hot and cold water valves. A copper-constantan thermocouple and a precision platinum resistance thermometer (Minco model S37-2) were calibrated by comparison with a National Bureau of Standards-calibrated Leeds and Northrup model 8164 platinum resistance thermometer. The thermometer was used to sense the temperature within the calorimeter bucket the thermocouple sensed the jacket temperature. A mercury-in-glass thermoregulator (Philadelphia Scientific Glass model CE-712) was used to control the jacket temperature. 

If the vapor pressure of liquid nitrogen is used for the temperature measurement, one allows N2 gas to condense in chamber B and the N2 pressures can be read directly on a pressure gauge. If a copper-Constantan thermocouple or a platinum resistance thermometer is used, it must be well calibrated, since accurate absolute temperatures are needed. If chamber B is not used, all further instractions concerning it may be disregarded. 

For the drop technique, the isoperibolic calorimeters are most frequently used. The calorimetric device consists of two main parts a furnace and a heated block. Between the calorimetric block and the furnace, there is a system of shields controlled by a mechanic, hydraulic or electromagnetic device, which prevents the heat transfer from the furnace to the calorimetric block. The calorimeter is made of copper with a cavity closed by a shield. A resistance thermometer wound on the block measures its temperature. Such a calorimeter can work up to 1700°C, especially when the furnace... 

Another type of resistance thermometer uses metal oxides, instead of metals it is frequently referred to as a thermistor. Electrical resistance of these metal oxides changes rapidly with even rather small temperature changes. Hence, thermistors are often emplyed to measure small temperature changes such as 1°C to 5 °C. The thermistor proper tends to have low purchase prices. Metal oxides, which are semiconductors, include mixtures of the following oxides nickel, manganese, copper, cobalt, tin, germanium, etc. [1]. 

Resistive materials used in thermometry include platinum, copper, nickel, rhodium-iron, and certain semiconductors known as thermistors. Sensors made from platinum wires are called platinum resistance thermometers (PRTs) and, though expensive, are widely used. They have excellent stability and the potential for high-precision measurement. The temperature range of operation is from -260 to 1000°C. Other resistance thermometers are less expensive than PRTs and are useful in certain situations. Copper has a fairly linear resistance-temperature relationship, but its upper temperature limit is only about 150°C, and because of its low resistance, special measurements may be required. Nickel has an upper temperature limit of about 300°C, but it oxidizes easily at high temperature and is quite nonlinear. Rhodium-iron resistors are used in cryogenic temperature measurements below the range of platinum resistors [11]. Generally, these materials (except thermistors) have a positive temperature coefficient of resistance—the resistance increases with temperature. 

The sample container, suspended in the calorimeter by a small tube, was constructed of copper and had a capacity of about 106 ml. Tinned copper vanes were arranged radially from the central reentrant well, containing a heater and a platinum resistance thermometer, to the outer wall of the... 

In this study, the heat capacities of Ti, Zr, and Hf were measured using a vacuum calorimeter. The zirconium sample was placed in a copper capsule that was fitted with an external heater winding and a re-entrant thermometer as well as a small amount of helium gas to ensure heat transfer. The temperature was measured with a calibrated platinum resistance thermometer and measurements were taken from 20 to 200 K. The purity of the Zr was 99.5%, the major impurity being Na. 

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