Temperature meters

The oscillation amplitude is too small (typically, 100 pm) to cause damage to the meter. Because the excitation current is also very small, intrinsically safe CMF versions are available for use in hazardous areas. The electronics can be mounted on the flowmeter directly, forming one compact unit, or the flowmeter can be interfaced to the electronics via a cable. The remote assembly may be necessary for high-temperature meters, or it may be convenient if the sensor is installed in a place that is not easily accessible. 

Presently, resistance thermometers are the most suitable temperature meters because of their high precision and stability. Mainly, they are used when resistance elements are wound directly on the surface of the calorimetric vessel and cover. Change of resistance with temperature can be in the current range of the temperature change of the calorimeter (less than 3 K) regarded as linear. 

Figure 7.26 The HD 2106 conductivity-temperature meter (Reproduced by permission of...

Industrial analysers can control physical or chemical parameters. Physical parameter analysers (conductimeters, viscometers, refractometers, pressure and temperature meters) frequently measure and control only one property of the fluid, the variation of which generally depends on a single component that is controlled In an indirect fashion. Chemical parameter analysers directly measure the concentration of one or more species In a fluid. They can be specific for a given species (e.g. pH-meters, potentiometers with Ion-selective electrodes, oxygen meters) or control several species simultaneously (e.g. gas or liquid chromatographs) or successively (photometers) with minimum alterations. 

When carrying out a batch distillation on a binary mixture it is very useful to have a quick and user-friendly analysis of the overheads. It is even better if the analysis can be performed on the plant without the need to take a sample to the laboratory and the process operator has a continuous record of the progress of the batch. A record of this sort can be provided by an on-line specific gravity (i.e. density corrected for temperature) meter. Many binary pairs such as mixtures of methanol, acetone and THF with water have large density differences between the organic distillate and water. This property can be used to control the split between reflux and product flow rates. 

Combined instrument Car speed odometer, engine speed indicator, water temperature meter, fuel gage... 

Cross section test points (B-) were measured by using WRN-type K thermocouple with temperature measuring range -50-400 °C, and temperature measurement accuracy 0.75% 2.5 °C. TES-1310 digital temperature meter was used as a monitor with resolution 0.1 °C, temperature measuring range -50 °C 199.9 C, and temperature measurement accuracy (0.3%-hl °C). 

Figure 4.4.3. Schematic diagram of a modem absolute vapor pressure apparatus T - temperature meter, P - vapor-pressure meter, V - vacuum meter, Z - measuring cell, M - magnetic stirrer, GI and Gil - degassing units for the solvent and for the polymer. ptq)rinted with permission from Ref 58, Copyright 1990,Wiley-VCH].

A typical temperature sequence for injection molding DMC would be feed hopper and feed zone - ambient temperature metering section 50-60°C nozzle 80-90°C mould temperature 135-185°C for polyester DMC or 160-22°C for epoxy DMC injection pressure 80-160 MPa. Cure time is generally of the order of 10-20 s per millimetre of wall thickness. Very little finishing of moldings is necessary. 

Comment this is the most commonly used temperature meter in the industry (Pt-100). It has a platinum resistance of 100 ohm at 0 °C. Moderately priced and delivers a signal. 

Heat-Prober, Handheld temperature meters, Wahl Instruments Inc. 

The fuel temperature meters, 19M1 and 19M2, use chromel-alumel (type K) thermocouples imbedded in the instrumented fuel elements as sensors. 19M2 allows selection of any of the fuel element thermocouples for readout only, while 19M1 has a scram at 400°C and an alarm at 34 0 °C. These instruments are also equipped with upscale burnout, and thus will read full scale if the thermocouple opens. They will read 0°C if the input is shorted. 

The outlet temperature of the medium to be heated should be controlled. This occurs with control valve AAlOl in combination with the temperature meter TlCA-i- (CTOOl). In case the measured temperature value exceeds the preset target value, the control valve will be activated more or less depending on the adjusted control characteristic and the control deviation. Thus the steam quantity fed to the heat exchanger will be reduced. 

Coprecipitation process to achieve doped nickel hydroxides 1,2,3 and 4 are inlets for precursors including pH adjuster, 5 is the outlet to fix the stirrer, 6 is the temperature meter, 7 is the mixture of the solutions, and 8 is the outlet for the precipitated hydroxides. 

An fuel-air mixture explosion can be initiated by a sudden discharge of static electricity. Yet, while flowing in systems, a fluid develops an electrical charge which will take as long to dissipate as the fluid is a poor conductor. The natural electrical conductivity of jet fuel is very low, on the order of a few picosiemens per meter, and it decreases further at low temperature. 

The most important factor for maturation and hydrocarbon type is therefore heat. The increase of temperature with depth is dependent on the geothermal gradient which varies from basin to basin An average value is about 3°C per 100 meters of depth. 

In order to carry out a distillation, the apparatus is completely assembled, the water pump turned on to its maximum capacity, and the screw clip on the capillary tube in the Claisen flask adjusted so that a gentle stream of air bubbles through the liquid (see Section 11,19 for details of the preparation of the capillary tube). The barometric pressure is read, and if the resulting vacuum deter mined from the reading on the mano meter is satisfactory (as estimated from the temperature of the tap water), the flask may be heated in an air (Fig. II,... 

Altitude in Meters Mean Temperature of Air Column in Centigrade Degrees ... 

The SI unit of viscosity is pascal-second (Pa s) or newton-second per meter squared (N s m ). Values tabulated are mN s (= centipoise, cP). The temperature in degrees Celsius at which the viscosity of a... 

The dynamic viscosity, or coefficient of viscosity, 77 of a Newtonian fluid is defined as the force per unit area necessary to maintain a unit velocity gradient at right angles to the direction of flow between two parallel planes a unit distance apart. The SI unit is pascal-second or newton-second per meter squared [N s m ]. The c.g.s. unit of viscosity is the poise [P] 1 cP = 1 mN s m . The dynamic viscosity decreases with the temperature approximately according to the equation log rj = A + BIT. Values of A and B for a large number of liquids are given by Barrer, Trans. Faraday Soc. 39 48 (1943). 

The temperature compensator on a pH meter varies the instrument definition of a pH unit from 54.20 mV at 0°C to perhaps 66.10 mV at 60°C. This permits one to measure the pH of the sample (and reference buffer standard) at its actual temperature and thus avoid error due to dissociation equilibria and to junction potentials which have significant temperature coefficients. 

A pH electrode is normally standardized using two buffers one near a pH of 7 and one that is more acidic or basic depending on the sample s expected pH. The pH electrode is immersed in the first buffer, and the standardize or calibrate control is adjusted until the meter reads the correct pH. The electrode is placed in the second buffer, and the slope or temperature control is adjusted to the-buffer s pH. Some pH meters are equipped with a temperature compensation feature, allowing the pH meter to correct the measured pH for any change in temperature. In this case a thermistor is placed in the sample and connected to the pH meter. The temperature control is set to the solution s temperature, and the pH meter is calibrated using the calibrate and slope controls. If a change in the sample s temperature is indicated by the thermistor, the pH meter adjusts the slope of the calibration based on an assumed Nerstian response of 2.303RT/F. 

Peel tests are accompHshed using many different geometries. In the simplest peel test, the T-peel test, the adherends are identical in size, shape, and thickness. Adherends are attached at thek ends to a tensile testing machine and then separated in a "T" fashion. The temperature of the test, as well as the rate of adherend separation, is specified. The force requked to open the adhesive bond is measured and the results are reported in terms of newtons per meter (pounds per inch, ppi). There are many other peel test configurations, each dependent upon the adhesive appHcation. Such tests are well described in the ASTM hterature. 

Dry Spinning. On a worldwide basis, about 90% of all spandex fibers are produced by various adaptations of dry spinning (15,16). The solution dry spinning process is illustrated in Figure 5. The polymer spinning solution is metered at a constant temperature by a precision gear pump... 

A.m blent Environment. The environment around the flow conduit must be considered in meter selection. Such factors as the ambient temperature and humidity, the pipe shock and vibration levels, the avadabiHty of electric power, and the corrosive and explosive characteristics of the environment may all influence flow meter selection. Special factors such as possible accidental flooding, the need for hosedown or steam cleaning, and the possibiHty of lightning or power transients may also need to be evaluated. 

Measurement Requirements. Any analysis of measurement requirements must begin with consideration of the particular accuracy, repeatabihty, and range needed. Depending on the appHcation, other measurement considerations might be the speed of system response and the pressure drop across the flow meter. For control appHcations repeatabihty may be the principal criterion conversely for critical measurements, the total installed system accuracy should be considered. This latter includes the accuracy of the flow meter and associated readout devices as well as the effects of piping, temperature, pressure, and fluid density. The accuracy of the system may also relate to the required measurement range. 

Positive-displacement meters are normally rated for a limited temperature range. Meters can be constmcted for high or low temperature use by adjusting the design clearance to allow for differences in the coefficient of thermal expansion of the parts. Owing to small operating clearances, filters are commonly installed before these meters to minimize seal wear and resulting loss of accuracy. 

A number of meter designs have been developed based on this principle. Some are shown in Eigure 17. Certain advantages ate claimed for each, but all share a number of characteristics. Perhaps the most important property is a full-scale deflection on the order of 0.001 mm. The sensors for these meters are extremely sensitive, stable, and capable of being temperature compensated. 

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