Response time, determination

For vapour detection there are three aspects that are modelled sensitivity, response time, and regeneration. The sensitivity determines at which concentration level the detector will respond. The theoretical detector output (alarm or no alarm) is calculated by comparing the input data (concentration, relative humidity) with empirical detector display outputs, obtained during controlled exposure laboratory experiments. The response time determines how long it takes before the detector actually shows the response and it depends on the concentration level. The regeneration time determines how long it takes, after a positive detection, before the detector can do a new measurement. 

These are typical response times determined by the resistance and capacitance of the electrode. There are large variations in reported values. The response time can be reduced by coating the electrode by a thin conducting surface and electronically driving this shield together with the capacitance of the connecting cable. 

Figure 21 Shear stresses of the aiuminosilicale/silicone oil suspensions vs the frequency of applied electric field (0.3 kV/mm).. The particle conductivity of ASl and AS2 suspensions are 6.0 x 10 and 8.4 xlO " S/m. the response time determined on this figure is 0.6 ms tor ASl and 0.22 s for...

The response time is equal to the ZC product, where Cis the diode capacitance, or when using an integrating amplifier, the response time is determined by the closed loop gain. 

Enzyme immunosensors are employed for the determination of Hepatitis B surface antigen, IgG, alpha-fetoprotein, estradiol, theophylline, insulin [9004-10-8] and alburnin (69,70). However, these immunosensors generally have slow response times and slow reversibiUty (57). 

The initial measurement of electrical resistance must be made after considerable time. Phenomenological information has been determined based on the corrosion rate expected at what period of time to initiate readings of the electrical resistance. Since these values are based on experiential fac tors rather than on fundamental (so-called first) principles, correlation tables and lists of suggested thicknesses, compositions, and response times for usage of ER-type probes have developed over time, and these have been incorporated into the values read out of monitoring systems using the ER method. 

Cg pH-sensitive film had a dynamic range from 6 to 8 and Cg-film responded at higher pH values (8-10).The membranes showed good reproducibility, reversibility and a short response time (<10 s). They also can be used for at least 3 months without any considerable absolution deviations. These sensors can be used for direct determination of pH in drinking water detergent and dishwasher liquid that have good agreement with pH meter data. 

Fig. 3-8 Circuit for determining the response time of measuring instruments with internal resistance R...

The time constant is one way of determining the dynamic features of a measurement system. Not all instrument manufacturers use the time constant some use the response time instead. The response time is the time between a step change of the measured quantity and the instant when the instrument s response does not differ from its final value by more than a specified amount.The response time is defined according to a deviation from the final value. Often response times for the relative deviation of 1%, 5%, 10%, or 37% are used. The corresponding response times are denoted by 99%, 95%, 90%, or 63% response time, respectively. The response time for a first-order system can be solved from Eq. (12.15). Note that the 63% response time of a first-order system is the same as the time constant r of the system. 

If your service is maintenance, you need to monitor the restoration and response times and determine your performance. You will also need to verify that the maintenance performed was effective by monitoring the incidence of recall to fix. 

Set up a mechanism for analyzing service reports so as to determine response times, time to repair, and total downtime. 

One possible complication to consider in functional experiments is the dependence of response on time. If fade occurs in the response, time becomes an important factor in determining the magnitude of response. 

Actifed is a medicinal preparation in which the effective components are the two drugs pseudoephedrine hydrochloride and triprolidine hydrochloride. The absorption spectrum of Actifed tablets dissolved in 0.1M hydrochloric acid is similar to that shown in Fig. 17.14(a) which is clearly of no value for quantitative determinations. A second derivative spectrum however is similar in character to that shown in Fig. 17.14(6) in which peak C corresponds to the pseudoephedrine hydrochloride and D to the triprolidine hydrochloride and from which it is possible to make quantitative measurements. Experience showed that it is advisable to use different response times for the two peaks with the instrument used a response setting of 3 was found to give the best results for pseudoephedrine hydrochloride, whilst a setting of 4 was best for the triprolidine hydrochloride. 

Resolution, analysis complicated by insufficient, 201 of x-rays, 61, 113-115 Response time of multiplier phototube, 57 Rhenium, determination by x-ray emission spectrography, 328 Rhodium, determination by x-ray emission spectrography, 328 Risk, consumer, 215 producer, 215... 

Calibration. In general, standards used for instrument calibration are physical devices (standard lamps, flow meters, etc.) or pure chemical compounds in solution (solid or liquid), although some combined forms could be used (e.g., Tb + Eu in glass for wavelength calibration). Calibrated lnstr iment parameters include wavelength accuracy, detection-system spectral responsivity (to determine corrected excitation and emission spectra), and stability, among others. Fluorescence data such as corrected excitation and emission spectra, quantum yields, decay times, and polarization that are to be compared among laboratories are dependent on these calibrations. The Instrument and fluorescence parameters and various standards, reviewed recently (1,2,11), are discussed briefly below. 

Another useful standard Is SRM 1647, priority pollutant polynuclear aromatic hydrocarbons (in acetonitrile). It can be used to calibrate liquid chromatographic Instruments (retention times. Instrument response), to determine percent recoveries, and to fortify aqueous samples with known PAH concentrations. Figure 8 Illustrates the HPLC separation and UV detection (fluorescence is also used extensively) for the 16 priority pollutants. 

A study that examined the interaction between exposure concentration and time of exposure on nervous system function found that concentration, rather than time of exposure, was more important in determining effects (Bushnell 1997). Rats were trained to press two levers for food reward one lever when a light flashed, the second lever produced food when there was no signal. The trained rats were exposed to 0,400, 800, 1,200, 1,600,2,000, or 2,400 ppm trichloroethylene for 0.33, 0.67, or 1 hour. Response times were signiflcantly increased only at 2,400 ppm at 0.67 and 1 hour. Sensitivity was significantly decreased at 2,400 ppm at all exposure times. At 0.33 hour, sensitivity was not affected at the other concentrations. At 0.67 hour, sensitivity was significantly decreased at 2,000, and 1,200 ppm, and at 1 hour, sensitivity was... 

The concept of a biocatalytic membrane electrode has been extended to the use of a tissue slice as the catalytic layer. An example of this approach is an electrode for AMP which consists of a slice of rabbit muscle adjacent to an ammonia gas electrode. NHj is produced by enzymatic action of rabbit muscle constituents on AMP The electrode exhibits a linear range of 1.4 x 10 to 1.0 x 10 M with a response time varying from 2.5 to 8.5 min, depending on the concentration. Electrode lifetime is about 28 days when stored between use in buffer with sodium azide to prevent bacterial growth. Excellent selectivity enables AMP to be determined in serum. 

For the detection of slow-acting biological agents (which may not produce symptoms for several days), the system response time would depend on the frequency of sampling and analysis. The frequency of sampling and analysis would be determined by factors such as the cost of the assay, the frequency with which critical reagents need to be replaced, the robustness of the detector, and so on. The minimum response time would be determined by the time required to collect a sample, prepare it for analysis, conduct the assay, and report the results. In the event of an alarm from a detector with a significant false-alarm rate, additional time would be required to determine its validity and to decide on an appropriate response. 

Good results are obtained for electrodes with sulphides of Pb, Cd and Cu(II), but with certain other sulphides the response time is unsatisfactory. Interference occurs in highly acidic solutions (H2S formation) and in alkaline solutions (at pH > 11) other metal ions sometimes disturb determinations with the metal ISE also, anions may cause difficulties, e.g., in a Cu(H) determination at a Cu(H) ISE if Cu2+ and Cl" are simultaneously present in the... 

Orion Model 95-64). In practice, one simply determines E ntot by calibration with a standard solution without the necessity of knowing the various constants mentioned. The S02 electrode allows the determination of concentrations down to 10 8 Af with a response time of a few minutes. From the above it appears that the gas-sensing electrodes show Nemstian behaviour provided that the concentrations to be measured are not high there is little or no interference by other components in the sample solution. 

The basis for the different response times of these probes is their response mechanism. In order to produce a change in fluorescence, a change in electric field must induce some movement either of the dye molecule as a whole or of its electrons. The degree of movement determines the speed of the fluorescence response. 

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