Process measurements accuracy

For process measurements, accuracy as a percent of span is the most common. 

Consistency sensor calibration Measurement of fiber or filler consistency is one of the most demanding process measurements. Accuracy has to be very high for control purpose but consistency meters are sensitive to a lot of process parameters like gas content, flow rates, etc. Therefore wet end control comprises a means to improve the calibration of consistency meters, by taking other process parameters into account. Thus the advanced consistency sensor calibration uses a soft sensor calibration technique. 

Process Measurements. The most commonly measured process variables are pressures, flows, levels, and temperatures (see Flow LffiASURELffiNT Liquid-levell asurel nt PressureLffiASURELffiNT Temperaturel asurel nt). When appropriate, other physical properties, chemical properties, and chemical compositions are also measured. The selection of the proper instmmentation for a particular appHcation is dependent on factors such as the type and nature of the fluid or soHd involved relevant process conditions rangeabiHty, accuracy, and repeatabiHty requited response time installed cost and maintainabiHty and reHabiHty. Various handbooks are available that can assist in selecting sensors (qv) for particular appHcations (14—16). 

Temperature. Temperature sensor selection and installation should be based on the process-related requirements of a particular situation, ie, temperature level and range, process environment, accuracy, and repeatabiHty. Accuracy and repeatabiHty are affected by the inherent characteristics of the device and its location and installation. For example, if the average temperature of a flowing fluid is to be measured, mounting the device nearly flush with... 

Accuracy and Repeatability Definitions of terminology pertaining to process measurements can be obtained from standard S5I.I from the International Society of Measurment and Control (ISA) and standard RC20-II from the Scientific Apparatus Manufac turers Association (SAMA), both of which are updated periodically. An appreciation of accuracy and repeatability is especially important. Some apphcations depend on the accuracy of the instrument, but other apphcations depend on repeatability. Excellent accuracy imphes excellent repeatabihty however, an instrument can have poor accuracy but excellent repeatability. In some apphcations, this is acceptable, as discussed below. 

The flow capacity of the transducer can be increased bv adding a booster relav like the one shown in Fig, 8-7.3/ , The flow capacity of the booster relav is nominally fiftv to one hundred times that of the nozzle amplifier shown in Fig, 8-7.3 3 and makes the combined trans-diicer/booster suitably responsive to operate pneumatic actuators. This type of transducer is stable into all sizes of load volumes and produces measured accuracy (see Instrument Society of America [ISA]-S5l, 1-1979, Process Instrumentation Terminology for the definition of measured accuracy) of 0,5 percent to 1,0 percent of span. 

The assessor should also find out whether an effective testing program is in place to help ensure the serviceability of process measurement equipment. The successful toller should have an established calibration program to address the accuracy of critical measurement equipment. Safety critical process parameters should be monitored and critical process equipment should automatically interlock when monitoring instrumentation detects safety critical deviations. Interlocks should either facilitate a remedy to the critical deviation or bring the process to the zero energy state. These instruments and interlocking devices should be routinely tested to ensure operational reliability. 

The establishment of performance criteria for a given tumor marker test is not a simple process because accuracy and precision are unique for each type of analyte and its application. Establishing methodological limits for accuracy, precision, sensitivity, and specificity often requires standard reference materials, quality control materials, comparative studies, and actual clinical specimens. Accuracy and precision must be measured over the analyte reportable range for which the device is intended to be used. Sensitivity and specificity must be considered with respect to the intended clinical use of the device. Also, the indications for use should be carefully considered in the design of the study protocol. The indications for class II should be to monitor residual tumor after surgery (or radiation), the recurrence of tumor, or response to therapy. A 510(k) must provide clear evidence that the device is accurate, safe, effective, and substantially equivalent to a device legally marketed in the United States. 

Inadequate knowledge of the process models and poor estimation of process parameters (physical properties, processing constants, etc.) mean that any technique for correcting the measurements should rely on simple, well-known, and indubitable process relationships, which should be satisfied independent of the measurements accuracy. Such relationships are the multicomponent mass and energy balances. 

In some manufacturing process analysis applications the analyte requires sample preparation (dilution, derivatization, etc.) to afford a suitable analytical method. Derivatization, emission enhancement, and other extrinsic fluorescent approaches described previously are examples of such methods. On-line methods, in particular those requiring chemical reaction, are often reserved for unique cases where other PAT techniques (e.g., UV-vis, NIR, etc.) are insufficient (e.g., very low concentrations) and real-time process control is imperative. That is, there are several complexities to address with these types of on-line solutions to realize a robust process analysis method such as post reaction cleanup, filtering of reaction byproducts, etc. Nevertheless, real-time sample preparation is achieved via an on-line sample conditioning system. These systems can also address harsh process stream conditions (flow, pressure, temperature, etc.) that are either not appropriate for the desired measurement accuracy or precision or the mechanical limitations of the inline insertion probe or flow cell. This section summarizes some of the common LIF monitoring applications across various sectors. 

When base selection and proofreading are combined, DNA polymerase leaves behind one net error for every 106 to 108 bases added. Yet the measured accuracy of replication in E. coli is higher still. The additional accuracy is provided by a separate enzyme system that repairs the mismatched base pairs remaining after replication. We describe this mismatch repair, along with other DNA repair processes, in Section 25.2. 

For the process measurement and control instrumentation the loop schedule enables allocation of a unique identifier (tag number) to each instrument used in the operation of the plant. This will allow application details to be added to the schedule (e.g., range, accuracy, set-point tolerance, signal type, description, location and any other information thought necessary to provide a clear understanding of the requirements for each instrument). 

Accuracy and Repeatability Definitions of terminology pertaining to process measurements can be obtained from standards available from the Instrumentation, Systems, and Automation Society... 

The reliability of the process measurements1 data is extremely important for good monitoring, control and optimization of chemical process. On-line rectification of a measurement error is possible be it a random error or a gross bias, if additional information is available. Such information is supplied by the extent to which the material and energy balances are satisfied by the recorded data. These balances are simple, involve parameters usually well known, and they should be satisfied independently of the measurements accuracy. 

MALDI differs from ESI in two major aspects (a) the MALDI ionization process is not continuous, but is a pulsed event, and (b) while the analytes for ESI are dissolved in the appropriate solvent and introduced into the ionization source, the MALDI analytes are dissolved and mixed with a solution of the appropriate matrix and then are cocrystallized with the matrix. Sensitivity for both techniques enables analyses at the low femtomole range (and even below), although most analyses are conducted at the low picomole range because of the greater convenience of sample handling at this level. Mass measurement accuracy, as indicated elsewhere in this discussion, depends on the choice of analyzer. These techniques are complementary and neither has exhibited dominance in the analysis of biological molecules. 

The test procedure shall represent the real world operation of slow heat release appliances burning wood and take into account the transient parameters of a batch wise burning combustion process. It shall fulfill typical test laboratory requirements such as reproducibility of the results, laboratory independence, measuring accuracy and simple test procedures. The test procedure shall support the wood appliance industry for their high quality products and should have a good relation of price and performance. The test procedure shall refer as much as possible to existing international (ISO) and European (CEN, Austrian standards) test standards. 

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