System errors

Fig. 4.41 Angular positional control system. = Error detector gain (V/rad) K2 = Amplifier gain (A/V) Kj = Motor constant (Nm/A) n = Gear ratio Hi = Tachogenerator constant (Vs/rad) H = Load moment of inertia (kg m ) Q = Load damping coefficient (Nms/rad).

All elosed-loop eontrol systems operate by measuring the error between desired inputs and aetual outputs. This does not, in itself, generate eontrol aetion errors that may be baek-propagated to train a neural network eontroller. If, however, a neural network of the plant exists, baek-propagation through this network of the system error (r(lcT) — y(lcT)) will provide the neeessary eontrol aetion errors to train the neural network eontroller as shown in Figure 10.29. 

Error messages (display) Err Ambient out or range error flashing display System error HI / LO Object out of range cover symbol no cover attached battery symbol battery low i dead ... 

FIGURE 6.30 External standard calibration curve for clozapine obtained with a /tPLC system. Error bars represent + one standard deviation. 

FIGURE 6.32 Solubility values at different pH values for phenazopyridine and piroxicam samples obtained with a Nanostream PLC system (error bars represent + one standard deviation). Values are compared with reported values. Literature values adapted from cited manuscripts. 

Bias Systemic error as opposed to a sampling error. For example, selection bias may occur when each member of the population does not have an equal chance of being selected for the sample... 

Discuss the various means of minimising systemic errors with respect to the following aspects ... 

While the chance of a systemic error in the modeling is always possible, the greatest variability, and uncertainty, is in raw material cost for depolymerization and the valuation of the product. Roughly speaking, the variable conversion costs,... 

The current method measures water vapour indirectly based on oxygen measurements in wet and dry flue gas. There are two disadvantages with this solution (a) the measurement uncertainty is relatively high it is very sensitive to system errors, for example bad calibration (b) if hydrocarbons are present in the flue gas they will interfere with the water vapour analysis. 

A program called KF controls all of the devices integrated into the system. It is written in Zymark s EasyLab control language, and, once started, does not stop until the operator aborts the run (or unless a fatal system error occurs). 

Effect of Dust Storm Episodes on the Average Weekly Aerosol Concentrations. The total and fine gravimetric mass averaged over all sites for each week, is depicted in Figure 6. The error bars for the Owens Valley curves represent the standard deviation of the mean. The errors on the Mono Lake curve represent the sampling system error of 15%. The mean weekly values do not include the three dust storm episodes sampled separately, but do include several additional dust storms. Table I lists all the dust storms reported by the sampler operators. 

Error bars are standard error of the mean. Also included for reference is the weekly mass concentration measured at the Mono Lake sampling site. Error bars are 15% measurement system error. 

Figure 7. Total mass (particles less than 15 fUn) and fine mass (particles less than 2.5 fjm) measured during 3 dust storms April 6-7, April 16-17, and April 23-24, 1979. Error bars are 15% measurement system error.

Today, clinical trials must adhere to nationally and internationally agreed codes of good clinical practice, which define ethical and scientific standards. Good clinical trial design and conduct should apply scientific methods. Skilful analysis can never correct for poor design. The purpose of the trial should be defined and specific hypotheses stated in the written study protocol, which will also include details of how the trial will be conducted. Errors in the data have two components, purely random errors and systemic errors or bias, which are not a consequence of chance alone. Randomisation of subjects is important both to avoid observer bias and to prevent or minimise the influence of unknown factors that might influence the results. 

The percent recoveries of 20 compounds from all 16 experimental runs are listed in Table III. The results for the seven remaining compounds in the mixture are not listed because either they were not recovered at all in any of the extractions (dimethylformamide and dimethyl sulfoxide), or because determinate system errors were discovered in the experimental protocol and rendered the data for those compounds unreliable. 

This means for improvement concerns the experimental procedures that are used to collect and analyze the calibration samples. In PAC, sample collection can involve either a highly automated sampling system, or a manual sampling process that requires manual sample extraction, preparation, and introduction. Even for an automated data collection system, errors due to fast process dynamics, analyzer sampling system dynamics, non-representative sample extraction, or sample instability can contribute large errors to the calibration data. For manual data collection, there are even more error sources to be considered, such as non-reproducibility of sample preparation and sample introduction to the analyzer. 

In order to remedy problems quickly or to avoid system errors, appropriate procedural controls must be applied to (a) enable early identification of an imminent breakdown, and (b) initiate appropriate preventive action. The next section suggests a course of action to follow to identify, analyze, and record computer system incidents, and to implement and test the corrective action taken. 

The errors inherent in any physical measurement are of two kinds. The first category, which is relatively simple to deal with, involves errors that are random. The second category, which is more difficult to detect and so also difficult to handle, includes systematic errors, i.e., errors which are not random but inherent in the reaction studied or the methods employed. A typical example of the latter would be the small contribution of a secondary reaction, the extent of which is determined by the concentrations and temperatures. It is thus inherent in the nature of the system observed, and the magnitude of the errors involved in neglecting this secondary reaction is not random but directly related to the state of the system. Errors due to small amounts of secondary reactions are the most frequent type of systematic error encountered in kinetic studies. ... 

Instruments run on last known set-point, alarm conditions are not received by control system Error will not automatically alarm on control system if last received process parameter within acceptable range... 

The outcome of the Source Code Review will be a report providing an overview of the review, together with a list of all observations noted and all actions that must be completed. Specific statements on software structure, programming practice, GMP-related functionality, information transfer with other portions of the system or other systems, error handling, redundant code, version control, and change control should be made before an overall conclusion on the suitability and maintainability of the software is drawn. A copy of annotated software listings should be retained with the report. 

Disk Filling Grade System Error Message... 

Error count increased by severe system error (defined in the tool)... 

Procedures should be put in place to pick up possible system errors as well as human error or misuse. It is important to track trends and demonstrate proactive management of issues. Statistical analysis should be applied to data gathered. 

Test failures were attributed to a number of causes as illustrated in Figure 17.3. Operator error while executing the test case accounted for 1% of test failures. These tests were repeated once the error was understood. Incorrect setup also accounted for 1% of test failures. These tests too were repeated with the correct setup once the error was understood. Clarity problems with the test method and acceptance criteria accounted for 40% of test failures. Only the remaining 58% of tests did what they should have done, which is detect system errors. That is, 42% of test failure processing was avoidable if a more robust test process was adopted. Of the errors identified, 37% were classed as significant, and 63% as not significant. Resolution of these errors impacted specification and design documents. 

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