Thermometer quartz crystal

New types of thermometers include sensitive and reliable thermistors and quartz crystal thermometers. 

C, is a cylindrical glass vessel with a volume of 450 cm. The piezometer contains the solution and 330 gms of Hg. The top of the piezometer is fitted with a Taper joint for filling. A precision bore capillary, E, (2mm in diameter) is fitted to the bottom of the piezometer. The piezometer is suspended (6) in a brass or stainless steel pressure vessel, H. A glass boiler tube, J, encloses the upper portion of the capillary. The pressure vessel is filled with ethylene glycol which serves as a thermal and pressure medium. The entire apparatus is submerged in a constant temperature bath controlled to 0.001 C. The temperature inside the pressure vessel is monitored with a Hewlett-Packard quartz crystal thermometer (to determine when thermal equilibrium is reached after compression and decompression). 

Quartz Crystal Thermometer. The temperature coefficient of the resonant frequency of quartz (14-20 MHz), using the piezoelectric effect, is a function of temperature (1 kHz per degree). In the temperature range -80°C to 230°C, an electronically controlled quartz crystal thermometer can be accurate to 0.02°C and has a sensitivity of 10 microdegrees centigrade in temperature difference measurements. 

A quartz crystal thermometer sustains a capacitance if the frequency of the RLC circuit is precisely tuned to 14 or 20 MHz (depending on the exposed crystal faces). The quartz crystal will then transmit a very precise frequency, which has a temperature coefficient (typically 1 kHz per degree centigrade). If the temperature fluctuations are precisely compensated by a feedback heater circuit, then a quartz crystal oscillator is precise to about 1 part in 1.4 x 108. 

Another resonant-frequency thermometer is the quartz crystal resonator (Benjaminson and Rowland, 1972), which, if the crystal is properly cut, is quite linear from about 190 to 525 K. Although this thermometer has excellent resolution, it does exhibit hysteresis and drift. The principle of quartz crystal thermometry is based on the temperature dependence of the piezoelectric resonant frequency of a quartz crystal wafer of a given dimension. The angle of cut of the quartz crystal is selected to give as nearly a linear and yet sensitive correspondence between resonant frequency and temperature as possible. This angle of cut is referred to as an LC (linear coefficient) cut. The temperature sensitivity of the quartz crystal thermometer is about 1000 Hz/°C. 

For a quartz thermometer, the resonant frequency of a quartz crystal resonator is strongly related to the temperature variation. With high resolution, the temperature change can be directly determined from the frequency change of a quartz crystal thermometer. A quartz thermometer developed for use between -80 and 250°C [85] has a resolution of 0.1 mK. If used at the same temperature, a comparable precision can be achieved. However, with temperature cycling, hysteresis can reduce its repeatability. An accuracy of 0.05°C can be achieved with calibration. Nevertheless the temperature resolution for the quartz resonator is found to be less accurate at lower temperatures Over the temperature range from 4.2 to 400 K, the temperature resolution with the resonant frequency change for a YS cut quartz crystal thermometer drops from 1 kHz/K at 300 K to 80 Hz/K at 4.2 K [86]. 

Temperature sensing devices which have been used for cryoscopy include mercury-in-glass, platinum resistance, thermistor, thermocouple and quartz crystal thermometers. 

A quartz crystal thermometer is a particularly convenient device for measuring temperatures with a precision of about 10" K. The temperature sensitive oscillations of a quartz crystal, cut in a particular plane, are monitored and compared with a standard frequency source. The quartz... 

Finally, two other temperature-measuring devices are the quartz crystal thermometer, incorporating a quartz crystal whose resonance frequency is temperature dependent, and optical pyrometers, which are useful above about 1300 K to measure the radiant intensity... 

Quartz, since it is a piezoelectric and not a ferroelectric, has no hysteresis loss when it oscillates, thus quartz crystal oscillators are widely used as frequency control devices in radios, computers, and watches. Since the frequency is a function of the mass of the crystal, they can serve as deposition monitors (quartz crystal microbalances) with sensitivities of less than 1 ng. By functionalizing the surface to absorb specific gases, they can also act as chemical sensors. The temperature sensitivity of a quartz crystal oscillator can be minimized by choosing the cut of the crystal relative to the optical axis, which is necessary for its use as a frequency standard. On the other hand, a cut can be chosen to maximize the frequency dependence on temperature and quartz crystal thermometers with millikelvin resolution are available. 

Quartz crystals have been used as thermometers in calorimetry relatively recently. Their use is based on the fact that the resonance frequency of the quartz crystal cut in a certain orientation to the axis of its crystal structure depends on temperature, whereby the temperature dependence is high and almost linear. 

Quartz thermometer (measurement of the frequency of an oscillator, controlled by a quartz crystal with linear temperature dependence— resolution 0.(X)01 K, range 2(X) to 500 K). 

An adiabatic calorimeter is designed to have negUgible heat flow to or from its surroundings. The calorimeter contains the phase of interest, kept at either constant volume or constant pressure, and also an electric heater and a temperature-measuring device such as a platinum resistance thermometer, thermistor, or quartz crystal oscillator. The contents may be stirred to ensure temperature uniformity. 

Quartz Thermometers. Development of quartz crystal frequency thermometers continues. These devices use the small but highly reproducible variation of the natural vibration frequency of appropriately cut piezoelectric quartz samples. The sensors are compact and useful over a wide cryogenic range (4-400 K) with an accuracy within a few hundredths of a kelvin. There are, however, some problems with hysteresis and aging. 

Who among us does not enjoy the vision of a rainbow The spectral colors spread out across the sky inspire awe and pleasure no matter how many times we see them. For this reason, we have attempted to replicate rainbows artificially. We can go to any toyshop and find rainbow glasses, any rock shop and find rainbow quartz made by plasma ionization techniques. Jewelry and craft shops sell rainbow jewelry made by electroplating titanium or niobium oxide. Teachers use rainbow tubes with a universal indicator to demonstrate pH changes and acid-base reactions. Dye mixtures can be separated by rainbow electrophoresis and rainbow chromatography. Rainbow thermometers and toys are made from liquid crystals. Thermochromic materials can be heated to produce rainbow colors. Every toy shop is awash with rainbow colors, a phenomenon not available prior to the many inventions of the twentieth century [39]. 

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