Measuring ranges

Here presented results were acquainted predominantly by one-channel ten-level AE analyser IOC of the AED Laboratory Brno firm. This device is equipped by ten window threshold levels, defined fi-om top and bottom, the tenth level has not limitation fi-om top. Total dynamic range is 40 dB. The analyser enables continuous observation of total number of counts Nc, or number of counts per time unit and similar. Everything may be observed both in lull measured range and in individual levels. Range of measuring interval is SO ms up to 2500 ms. 

Because of the generality of the symmetry principle that underlies the nonlinear optical spectroscopy of surfaces and interfaces, the approach has found application to a remarkably wide range of material systems. These include not only the conventional case of solid surfaces in ultrahigh vacuum, but also gas/solid, liquid/solid, gas/liquid and liquid/liquid interfaces. The infonnation attainable from the measurements ranges from adsorbate coverage and orientation to interface vibrational and electronic spectroscopy to surface dynamics on the femtosecond time scale. 

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. 

Temperature measurements ranging from 760 to 1760°C are made usiag iron—constantan or chromel—alumel thermocouples and optical or surface pyrometers. Temperature measuriag devices are placed ia multiple locations and protected to allow replacement without iaciaerator shutdown (see... 

TABLE 8-7 Recommended Temperature Measurement Ranges for RTDs and Thermocouples... 

Total Radiation Pyrometers In total radiation pyrometers, the thermal radiation is detec ted over a large range of wavelengths from the objec t at high temperature. The detector is normally a thermopile, which is built by connec ting several thermocouples in series to increase the temperature measurement range. The pyrometer is calibrated for black bodies, so the indicated temperature Tp should be converted for non-black body temperature. 

The upper hmit of a gas concentration measurement range is usually 1.5 to 2.5 times the applicable emission limit. If no span value is provided, a span value equivalent to 1.5 to 2.5 times the expected concentration is used. For convenience, the span value should correspond to 100 percent of the recorder scale. 

Portable x-ray energy dispersive sulphur in oil analyser ASE-1 with measurement range 0.015 - 5% and a detection limit near 0.001%. SPARK-1-2M, BRA-17-02 and ASE-1 have been certified as measuring... 

The molecular absoi ption spectra, registered at a lower temperature (e.g. 700 °C for iodide or chloride of potassium or sodium), enable one to find the absorbance ratio for any pair of wavelengths in the measurement range. These ratios can be used as a correction factor for analytical signal in atomic absoi ption analysis (at atomization temperatures above 2000 °C). The proposed method was tested by determination of beforehand known silicon and iron content in potassium chloride and sodium iodide respectively. The results ai e subject to random error only. 

Notice on tliis graph that the 25°C experiments were informative, and results were in the measurable range. At 135°C some intermediate, semi-quantitative results could be seen. At 285°C no detectable adsorption could be seen. Taking the high adsorption result at 25°C as 22.4 mL/kg, this converts to 0.001 mole/kg. Compare this with the 0.22 mole/kg needed for measurable result in the CSTR case in the previous section. 

Smoke concentrations ranged from 0.3 to more than 4 mg m . Daily means of the sampling stations are shown in Fig. 18-4. Sulfur dioxide measurements ranged from less than 0.1 ppm (260 /rg m ) to 1.34 ppm (3484 /Ag m" ). Also, 4 of the 11 stahons had at least one daily value in excess of 1 ppm, and 9 of the 11 stations had at least one daily value in excess... 

The counting times required for measurement range between a few seconds and several minutes per element, depending on specimen characteristics and the desired precision. 

Substance Measuring range Max. operating time (hours)... 

TABLE 12.3 Contact Thermometers and Useful Measuring Ranges... 

The measurement range for platinum is -200 to +800 °C, for nickel -50 to +250 °C, and for copper -50 to +200 °C. The advantages are good accuracy, almost linear characteristics, and stability. A disadvantage is the small change of resistance with temperature, which requires a high sensitivity from the rest of the measurement equipment. 

The measurement range of a thermistor is dependent on the probe type, typically -100 to +300 °C. The stability is not as good as that of metallic resistances. Thermistors are not standardized like some of the metallic probes. The thermistor has the advantage of a high change of the resistance with temperature. A very wide variety of sizes and shapes and a low price makes them attractive in relation to the metrological performance. 

The measurement ranges for the base-metal thermocouples are 0 to +750 °C (type J), -200 to +1200 °C (type K), and -200 to +350 °C (type T). The noble-metal thermocouples can be used at higher temperatures up to 1700 °C. The dynamic response of sheathed thermocouples is not very fast however, a probe made from bare, thin wires can have very fast dynamic properties. One of the best features of thermocouples is the simplicity of making new probes by soldering or welding the ends of two wires together. 

The measurement range is dependent on the instrument but can cover the range -50 to +500 °C. The accuracy is not as high as the best contact thermometers. One reason for this is that the emissivity of the surface has an effect on the measurement result, and an emissivity correction is necessary for most instruments. The positive features are noncontact measurement and very fast dynamics, which enable a rapid scan of surface temperatures from a distance this is convenient when carrying out, for example, thermal comfort measurements. 

Capacitive sensors are small and rapidly respond to changes in air humidity. The measurement range is 0-100% RH. Due to the electrical principle, they can... 

The resistive measurement principle is based on a humidity-dependent electrical resistance. The early probes used lithium chloride as the hygroscopic resistive material. Such probes are still available under the name Dunmore sensors. The measurement range of such devices is quite narrow, and the resistance versus humidity relationship is extremely nonlinear. 

Recent developments are leading toward other materials like silica gel or polymers. Certain types of semiconductors are also used as resistive probes. The measurement range of resistive sensors varies depending on materials used. It can be as wide as 0-99% RH. The dynamics are fast enough for normal ventilation applications and the stability of good resistive sensors is high. This does not reduce the need for calibration, but the intervals of successive calibrations can be extended. 

The measured pressure differences in ventilation applications are low or very low. The measurement range varies from a few pascals to several thousand pascals. At the lower end are typically building leakage and air movement-related measurements, where only a few pascals can cause a remarkably large air-tlow. The largest pressure differences probably occur in fan performance determination and similar applications. This wide range requires special demands on the measuring equipment and selection of the correct instrument for each application (Fig. 12.15). 

A very obvious way to change die measurement range and sensitivity of a fluid manometer is by using fluids of different densities. There are only a few suitable liquids with specific gravit> between that of water and mercury. Ethylene bromide has a specific gravity of 2.2 and acetylene tetrabromide 3.0., but they are corrosive. 

The measurement range of a vane anemometer is typically between 0.3 and 30 m s E It may start rotating with slightly lower velocities, but due to the characteristic curve having a small nonlinear part in the low-speed end, the useful range is narrower. The actual precision depends on the quality of the instrument however, the inaccuracy may vary between 1% and 5% of the scale. The larger the vane, the higher the accuracy. 

Any obstruction inserted into a duct or pipe that creates a measurable pressure difference can be used as a flow meter. The three basic standardized flow measurement devices presented above are perhaps more suitable for laboratory work than installation as permanent ductwork instruments in ventilation applications. They are sensitive to flow disturbances, relatively expensive, require considerable space, and have a narrow measurement range and a high permanent pressure loss. For these reasons, numerous attempts have been made to develop instruments without these drawbacks. Some of them, like the... 

Some general quantitative characteristics (orders of magnitudes) of LDA systems are velocity measurement range 1 mm s -100 m s relative measurement uncertainty 0.1-1% rate of accepted data 0.1-10 kHz size of the optical probe 10 p.m-1 mm for each dimension measuring distance 0.1-1 m. 

Particle Collection Particles in the extracted partial volume flow are retained in the collector filter. Tlie particle mass emitted is determined by the weight difference of the filter before and after the collection. Factors crucial to the measuring precision and the smallest measuring range of particle concentration are ... 

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