Experimental error equipment accuracy

Our computer model predicted the Phase I test results with accuracy adequate for safety design even though there were experimental errors. To reduce these experimental errors. In Phase I I, we made some equipment modifications and used a larger reactor. 

Note that a number of complicating factors have been left out for clarity For instance, in the EMF equation, activities instead of concentrations should be used. Activities are related to concentrations by a multiplicative activity coefficient that itself is sensitive to the concentrations of all ions in the solution. The reference electrode necessary to close the circuit also generates a (diffusion) potential that is a complex function of activities and ion mobilities. Furthermore, the slope S of the electrode function is an experimentally determined parameter subject to error. The essential point, though, is that the DVM-clipped voltages appear in the exponent and that cheap equipment extracts a heavy price in terms of accuracy and precision (viz. quantization noise such an instrument typically displays the result in a 1 mV, 0.1 mV, 0.01 mV, or 0.001 mV format a two-decimal instrument clips a 345.678. .. mV result to 345.67 mV, that is it does not round up ... 78 to ... 8 ). 

Kinetic parameters from selected publication on CO2 reactivity are shown in Table 1. A wide span of apparent activation energies is published for biomass chars, 80.3 kJ/mol -318 kJ/mol and for coal chars, 79 kJ/mol -359.5 kJ/mol Some of the discrepancy can be explained as due to different experimental procedures (such as sample load, particle size and sample preparation) and the application of different analysing equipment. Concerning the latter one, the potential role of systematic errors in temperature measurements among various thermobalances is evident. Variations might also be explained by different extraction procedures, lack of accuracy caused by the approximations used in the different computational methods and the kinetic compensation effect. 

Error thus arises from two sources. Lack of precision (random errors) can be estimated by a statistical analysis of a series of measurements. Lack of accuracy (systematic errors) is much more problematic. If a systematic error is known to be present, we should do our best to correct for it before reporting the result. (For example, if our apparatus has not been calibrated correctly, it should be recalibrated.) The problem is that systematic errors of which we have no knowledge may be present. In this case the experiment should be repeated with different apparatus to eliminate the systematic error caused by a particular piece of equipment better still, a different and independent way to measure the property might be devised. Only after enough independent experimental data are available can we be convinced of the accuracy of a result— that is, how closely it approximates the true result. 

A number of factors limit the accuracy with which parameters needed for the design of commercial equipment can be determined. The kinetic parameters may be affected by inaccurate accounting for laboratory reactor heat and mass transport, and hydrodynamics correlations for these are typically determined under nonreacting conditions at ambient temperature and pressure and with nonreactive model fluids and may not be applicable or accurate at reaction conditions. Experimental uncertainty including errors in analysis, measurement,... 

Determinate error usually results from experimental equipment which is faulty. Students usually first meet this concept in the analytical chemistry laboratory in determinations of weight and volume. The quality of the equipment used is reflected in the accuracy of the results obtained. Accuracy is a measure of how close the experimental result is to the truth. For example, if one wishes to make up a solution of accurately known concentration in a volumetric flask of 100 mL, both the flask and the balance used must be carefully calibrated. The flask is calibrated by weighing it empty and then filled with distilled water at a known temperature. On the basis of the weight of water, and the known density of the water, one may calculate an accurate volume for the flask when it is properly filled to the mark. Calibration of the balance is based on the use of standard weights which do not corrode and which cover the range in mass used in the experiment. The accuracy of the standard weights and the quality of the volumetric flask determine the accuracy of the concentration of the solution which is made. 

The paper confirms the usefulness of ANNs for numerical description of liquid liquid phase equihbria of the ternary system. Taking into account difficulties in experimental conditions, comphcated measurement equipment and unavoidable errors of the devices used which limit the precision of the laboratory measurement results, the accuracy of the results generated by the network may be considered satisfactory for engineering calcrrlatiorrs. The properly selected and trained network of relatively simple structrrre (one hidden layer with 20 neirrones) rendered precisely, qualitatively and quantitatively, the thermodynamic character of the ternary system. 

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