Measurement procedures timing

Averaging time The time period over which the measuring procedure provides a single value. 

Both procedures measure the time for a fixed volume of the sample to flow though a calibrated tube at a controlled temperature. 

We have said that every time the calibration analyzes a new unknown sample, this amounts to an additional validation test of the calibration. It can be a major mistake to believe that, just because a calibration worked well when it was being developed, it will continue to produce reliable results from that point on. When we discussed the requirements for a training set, we said that collection of samples in the training set must, as a group, be representative in all ways of the unknowns that will be analyzed by the calibration. If this condition is not met, then the calibration is invalid and cannot be expected to produce reliable results. Any change in the process, the instrument, or the measurement procedure which introduces changes into the data measured on an unknown will violate this condition and invalidate the method If this occurs, the concentration values that the calibration predicts for unknown samples are completely unreliable We must therefore have a plan and procedures in place that will insure that we are alerted if such a condition should arise. 

Definition and Uses of Standards. In the context of this paper, the term "standard" denotes a well-characterized material for which a physical parameter or concentration of chemical constituent has been determined with a known precision and accuracy. These standards can be used to check or determine (a) instrumental parameters such as wavelength accuracy, detection-system spectral responsivity, and stability (b) the instrument response to specific fluorescent species and (c) the accuracy of measurements made by specific Instruments or measurement procedures (assess whether the analytical measurement process is in statistical control and whether it exhibits bias). Once the luminescence instrumentation has been calibrated, it can be used to measure the luminescence characteristics of chemical systems, including corrected excitation and emission spectra, quantum yields, decay times, emission anisotropies, energy transfer, and, with appropriate standards, the concentrations of chemical constituents in complex S2unples. 

Repeatability is the closeness of the agreement between the results of successive measurements of the same measurand carried out under the same conditions of measurement . Repeatability conditions include the same measurement procedure, the same observer, the same measuring instrument, used under the same conditions, the same location, and repetition over a short period of time (ISO 3534-1 [1993]). 

Fig. 3.1. Schematic diagram of a TCSPC setup. Using a fast timing device (e.g., time-to-amplitude-converter) the time is measured between the excitation pulse and the detection of a photon. By repeating this procedure many times a decay curve is measured. TAC time to amplitude convertor, MCA multi channel analyzer, PC personal computer. 

All six samples at both sites were prepared the same way. Five separate aliquots from each sample were separately sampled and prepared for testing. Each aliquot was then measured three times. Conditions and standard operating procedures for METHODS A and B were carefully specified for both Labs 1 and 2. 

Repeatability means conditions of measurement that includes the same measurement procedure, same operators, same measuring system, same operating conditions and same location, and replicate measurements on the same or similar objects over a short period of time. 

Dynamic ion separation systems are based on another physical principle and use the different flight time of ions with different masses and different velocity (e.g., in ToF mass analyzers). In addition, in dynamic ion separation systems there is a time dependent variation of one or more system parameters, e.g., changing of electrical or/and magnetic field strengths, which means the ion motion during the measurement procedure is crucial for the mass spectrometric analysis. 

Long-lived radionuclides occur at extremely low concentrations, especially in environmental samples, therefore several authors have proposed matrix separation and enrichment of the analytes before analysis.21,24,26,3 39 Radiochemical methods often require very careful and time consuming separation and enrichment processes and measurement procedures of a-, (3- and -emitting radioactive species at the trace and ultratrace level using conventional radioanalytical techniques 40-43 Trace/matrix separation, which is performed offline or online in order to avoid possible isobaric interferences, matrix effects and to reduce the detection limits for the determination of long-lived radionuclides, is also advantageous before ICP-MS measurements as the most widely applied mass spectrometric technique. 

Burning and Burning Characteristics of Propellants, Experimental Procedures, The simplest method for experimental detn of burning rate is to measure the time required for a long strand(or stick) of proplnt to burn in a closed vessel... 

There are several important points that need to be stressed. First, the estimation of discoloration in meat by measurement of percent metmyoglobin is useful in a relative sense only. Proper control samples (i.e., nontreated samples subjected to identical conditions, dilutions, and analyses, as treated samples) must be in place, and color measurement must occur in the same manner with both control and treated samples. Additionally, comparisons of values for percent metmyoglobin between different laboratories are only valid when investigators use the same measurement procedure. The use of three different formulas (i.e., from three different procedures) will yield different values for percent metmyoglobin. Again, it is the relative differences between treatments, or the changes over time, that become important, and... 

If multiple procedures are performed, a qualitative measure of time dependence can be gained. This is achieved by linking two ramps in an up-and-down sequence and examining the area of hysteresis. A second option is to connect three segments as an up ramp, a peak hold step, and a down ramp sequence this option has the effect of altering the area of hysteresis because the sample is broken down more effectively before the down step. 

In order to perform the on-line optimization strategy, the knowledge of current state variables and/or parameters in the process models is required. Due to the fact that some of these variables cannot be known exactly or sometime can be measured with time delay, it is essential to include an on-line estimator to estimate these process variables using available process measurements as well. The sequence of an estimation and optimization procedure is known as an estimation-optimization task [6], As in several estimation techniques, an Extended Kalman Filter (EKF) has become increasingly popular because it is relatively easy to implement. It has been found that the EKF can be applied to a number of chemical process applications with great success. Once the estimate of unknown process variables is deter-... 

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