Measurement skills

In 1901, the U.S. National Bureau of Standards (NBS) - now the National Institute of Standards and Technology (NIST) - was founded because of the increasing demand for various kinds of standards in the rapidly developing engineering industries. The early history of the NBS reference material program started in 1905 with a cooperative effort within the iron and steel industry whereby industrial analysts helped characterize the individual reference materials. Cooperation with NBS was recognized as a mark of achievement for the laboratory, so this effort served a dual purpose. It both helped the laboratory develop its measurement skills and also helped NIST understand the meastuement problems associated with a given matrix. 

Unlike thermochemical process safety, however, the bulk of the IH effort (its hazards assessment and risk analysis) falls elsewhere, as the toxicology and preventive measure skills are not in the bulk drug process development function at all. Nevertheless, the bulk drug development function does have some important roles to play in ensuring the IH safety of its processes. 

A single-dose study in 12 healthy subjects found that the pharmacokinetics of mirtazapine and diazepam were not affected by concurrent use, but diazepam further impaired the action of mirtazapine on objectively measured skill performance the combined actions were mostly additive. The impairment of psychomotor performance and learning caused by diazepam is increased by mirtazapine and therefore the manufacturers warn that the sedative effects of benzodiazepines in general may be potentiated by concurrent use with mirtazapine. ... 

Reverse engineering is a wonderful activity which can be conducted especially for mechanical engineering science students. Students will enjoy this session very much. It was observed that the model-measuring skills were also improved, since this activity is more practical and group involved than that of the traditional sketching. 

There are two types of measurement errors, systematic and random. The former are due to an inherent bias in the measurement procedure, resulting in a consistent deviation of the experimental measurement from its true value. An experimenter s skill and experience provide the only means of consistently detecting and avoiding systematic errors. By contrast, random or statistical errors are assumed to result from a large number of small disturbances. Such errors tend to have simple distributions subject to statistical characterization. 

Mercury porosimetry is generally regarded as the best method available for the routine determination of pore size in the macropore and upper mesopore range. The apparatus is relatively simple in principle (though not inexpensive) and the experimental procedure is less demanding than gas adsorption measurements, in either time or skill. Perhaps on account of the simplicity of the method there is some temptation to overlook the assumptions, often tacit, that are involved, and also the potential sources of error. 

Dip Stick Indicators. Visual level indication can be obtained by dropping a weighted cable or rigid dip stick into the media until it reaches the bottom of the vessel. Graduations are marked on the cable or stick. Upon retrieval the operator looks for the point of dry vs wet indicating the depth of the media. This method of level indication is useful in ambient/atmospheric appHcations in nonha2ardous environments. It is not recommended for other appHcations. Measurements are accurate only to the extent of the skill of the operator. 

Several types of secondary pyrometer are available. In addition to those that measure by varying lamp current, some pyrometers maintain the lamp at constant current but interpose a wedge of graduated neutral density, whose position is a measure of temperature. Also, automatic pyrometers are available in which the eye is replaced by a detector and the measuring element is operated by a servo. In general, the accuracy of the automatic pyrometer is somewhat less than that achieved manually by a skilled operator. 

The overall objective of research under way as of ca 1997 is to develop a system of sale by description for fine and medium wools whereby the buyer is presented only with measured data on the principal characteristics of the raw wool, as well as an assessment of the less important characteristics by an independent skilled appraiser (8). A scheme for assessing the risk of the presence of colored fiber content in greasy wool has been proposed which depends on production parameters and on the age and sex of the sheep (5). Instmmentation and computer algorithms for the measurement of style and handle... 

There are many techniques available for measuring the particle-size distribution of powders. The wide size range covered, from nanometers to millimeters, cannot be analyzed using a single measurement principle. Added to this are the usual constraints of capital costs versus running costs, speed of operation, degree of skill required, and, most important, the end-use requirement. 

Analysts The above is a formidable barrier. Analysts must use limited and uncertain measurements to operate and control the plant and understand the internal process. Multiple interpretations can result from analyzing hmited, sparse, suboptimal data. Both intuitive and complex algorithmic analysis methods add bias. Expert and artificial iutefligence systems may ultimately be developed to recognize and handle all of these hmitations during the model development. However, the current state-of-the-art requires the intervention of skilled analysts to draw accurate conclusions about plant operation. 

The procedure given in Fig. 30-15 leaves much to analysts. Criteria for selecting the number ana location of measurements for a particular piece of equipment or unit have not been established in the literature. Therefore, there is heavy reliance on examining alternative models at the bottom of the procedure. The creativity of analysts to develop alternative explanations for performance or hypotheses explaining why the present model might be wrong is a particularly important skill. 

The current and past operation should be compared so that the timing of the observed problems is estabhshed. The possible causes (hypotheses) can be compared against the measurements found on the log sheets. The number of possible causes can then be reduced. When the quantity or quahty or measurements is insufficient to further reduce the set of causes, additional measurements are required. These may require special instruments (e.g., gamma-ray scanning) not routinely usedin the plant. Alternative operating conmtions may also be required to further reduce the number of causes. As part of the problem identification, it is alwavs important to look for measurements that are inconsistent with the proposed explanation. They will be more informative than the ones justifying the hypothesized cause. Ultimately, with appropriate additional measurements, the cause can be identified. This is not an exact science and, as stated above, relies heavily upon the communication, technical, and investigative skills of analysts. 

A change in the measurements or parameters indicates a change in the unit operation. The diagnosis (interpretation) of the cause for the change requires troubleshooting skills. 

If the technical staff from the client company recognizes that a toller may be asked to perform new analyses and make operating decisions based upon the results, the client may help the toller develop the needed procedures and skills required to make these decisions. Typically a round robin laboratory qualification exercise will be performed. Samples of known standards and unknown concentrations of the materials to be analyzed for the toll will be prepared and sent to both laboratories. This can help ensure that equipment calibration is synchronized and that the toller is capable of performing accurate measurements. In some cases, the toller may be the party with the chemical, process, or synthesis specific expertise. 

Rapid advances in understanding the nature and behaviour of materials required both kinds of skill, in measurement and in theory, acting in synergy among metallurgists, this only came to be recognised fully around the middle of the twentieth century, at about the same time as materials science became established as a new discipline. 

It is often worthwhile for building staff to develop skills in making temperature, humidity, airflow, and CO2 measurements and assessing patterns of air movement (e.g., using chemical smoke). 

The use of tracers for airflow measurement in ventilation ducts is not very common. There are several reasons for this. Compared to other flow measurement methods, tracers require more complicated equipment, skilled personnel, and are more expensive. There are, however, situations when conventional measurement methods are not applicable. For instance, if the space available is small, and hence the flow meter cannot be installed, or if no space is free to carry out traversing measurements, the use of a tracer might be an alternative. 

An effective maintenance system depends upon it being adequately resourced. Maintenance resources include people with appropriate skills, replacement parts and materials, access to support from OEMs when needed, and the funds to purchase this material. If the equipment is no longer supported by the OEM, then you may need to cannibalize old machines or manufacture the parts yourself. This can be a problem since you may not have a new part from which to take measurements. At some point you need to decide whether it is more economical to maintain the old equipment than to buy new. Your inventory control system needs to account for equipment spares and to adjust spares holding based on usage. 

The analyst needs to develop a measure of skill in order to analyze the task effectively since the technique is not a simple procedure that can be applied immediately. However, the necessary skills can be acquired reasonably quickly through practice. 

---