Checking calibration

Calibrate for every batch Check calibration before change of service... 

Two separate flowmeter differentials should be read. These will probably have to be read with DP transmitter. It is suggested both DP units have one quality calibrated 6-in. gauge on transmitter output to directly read differential in %FS, FR, or psi. DP transmitters should be carefully bench-checked/calibrated, retaining indicated versus actual calibration data. 

Labelling and Calibration Check calibration certificate, indicate equipment identification details ... 

Silent-hours operation, which is commonly termed hands-off analysis, requires the automatic analysis to operate to a set protocol. For a fully automatic instrument to run in this manner, it will require a feedback system comparing the results with check cahbration standards. A calibration graph can be constructed from the analytical data, and the precision of this graph is easily evaluated. As the analyses proceed, the system can be monitored by reference to the check calibration standards. Should the performance remain within specification, the analyses can safely go on. The automatic instrument can then operate within the set protocols throughout the silent hours, taking full account of any variations in the instrument and its operating parameters. 

An initial calibration verification standard should be measured after calibration and before measuring any sample. A calibration verification standard is a standard solution or set of solutions used to check calibration standard levels. The concentration of the analyte should be near either the regulatory level of concern or approximately at the midpoint of the calibration range. These standards must be independent of the calibration solutions and be prepared from a stock solution with a different manufacturer or manufacturer lot identification than the calibration standards. An acceptance criterion is set, usually as a maximum allowable percentage variation (e.g., 5%, 10%). The calibration can be continually verified using either a calibration standard or the initial calibration verification standard. Acceptance criteria must be set and action taken when results fall outside the limits (i.e., stop the analysis, investigate, correct the problem and rerun samples run between the verification standards that were not limits). 

The discipline of analytical chemistry is wide and catholic. It is often difficult for a food chemist to understand the purist concerns of a process control chemist in a pharmaceutical company. The former deals with a complex and variable matrix with many standard analytical methods prescribed by Codex Alimentarius, for which comparability is achieved by strict adherence to the method, and the concept of a true result is of passing interest. Pharmaceuticals, in contrast, have a well-defined matrix, the excipients, and a well-defined analyte (the active) at a concentration that is, in theory, already known. A 100-mg tablet of aspirin, for example, is likely to contain close to 100 mg aspirin, and the analytical methods can be set up on that premise. Some analytical methods are more stable than others, and thus the need to check calibrations is less pressing. Recovery is an issue for many analyses of environmental samples, as is speciation. Any analysis that must... 

Reliability. Certain controls are only effective if carefully maintained. Whereas a substitution, if appropriately selected, may need monitoring, a control that depends on a sensor operating an alarm may cease to work after it is installed if it is not carefully checked, calibrated, and repaired. This procedure costs money, time, and supervisory effort, and increases risk. 

Calibration control standards (CCSs) are used to check calibration. The CCS is the first sample analyzed after calibration. Its concentration may or may not be known, but it is used for successive comparisons. A CCS may be analyzed periodically or after a specified number of samples (say, 20). The CCS value can be plotted on a control chart to monitor statistical control. 

In UV and visible vapor, bubbles cannot be tolerated in the sample, because they will generate noise in the optical reading, and if a pressurized cell is used, the cell pressure must be kept constant. Nitrogen or water is used to purge the cell, and interference or broadband filters are used for checking calibration. Photometers are normally used for single-component mea-... 

Maintenance procedures (spares, diagnostic checking, calibration)... 

Check calibration of DO probe in reservoir according to manufacturer s instructions and adjust if necessary. 

The variation of sensitivity between different sensors was also checked. Calibration curves with five different sensors were performed. A Relative Standard Deviation of 13, 13 and 42% of calibration slopes (sensitivity) were obtained for Cu, Pb and Cd respectively. These variations should have limited consequence on bias and precision when the standard addition method is used. However, for Cd, variations in the limit of quantification between two electrodes could be expected. Finally, the accuracy of the method was evaluated by the measurement of a SWIFT reference material used during the 2nd SWIFT-WFD Proficiency Testing exercise (Table 4.2.2). The reference value was chosen as the consensus value of the selected data population obtained after excluding the outliers. The performances of the device were estimated according to the Z-score (Z) calculation. Based on this score, results obtained with the SPEs/PalmSens method were consistent with those obtained by all methods for Pb and Cu ( Z < 2) while the result was less satisfactory for Cd (2 < Z < 3). 

The precision of analysis can be within 3 to 5% standard deviation if care is taken to check calibration curves frequently. Also, frequent maintenance of the burners is necessary to attain this precision consistently. 

Device not calibrated - recalibrate. Calibration curve deviates from linearity at high mass fractions - measure against known standard. Impurities in the stream - analyze a sample. Mixture is not all liquid - check sample. Calibration data are temperature dependent - check calibration at various temperatures. System is not at steady state - take more measurements. Scatter in data - take more measurements. 

For each system, procedures for preventative maintenance (including periodic calibration or revalidation) should be established. The objective of preventative maintenance is to check, calibrate or replace critical system components to prevent future failure and/or breakdown of the system, as this could have a negative effect on the quality of the product (or data). The following items need to be covered in the preventative maintenance procedure(s) ... 

The performance of a diagnostic X-ray machine should be checked at least annually with appropriate instruments by a qualified person. If the capability to do this is not available in-house, a qualified consultant should be hired to do the task. If any maintenance is done or if the machine is relocated, a survey should be undertaken for leakage radiation fromthe source. If the unit is moved to another facility, the exposure levels in the adjacent areas should be tested to ensure that the exposure levels are within the permissible limits forcontrolled and uncontrolled areas. Records of all maintenance, surveys, leakage checks, calibration, personnel monitoring, etc. should be maintained at the facility and at the radiation safety office. Because of the long latency period for cancer developing from radiation exposures, it would not be unreasonable to maintain personnel exposure records for up to 40 years. 

Numerical Simulation Techniques Parameterizing the Simulation Model Initial Numerical Simulation Results Sensitivity Checks Calibrating the Simulation Model Conclusion... 

Periodic check/calibration of Disassembly Basin level instrumentation... 

Standards Samples with values known by the analyst and used to calibrate equipment and to check calibration... 

In order to ensitre that safety system settings and limits and conditions for normal operation are met at all times, the relevant systems and components should be monitored, inspected, checked, calibrated and tested in accordance with an approved smveillance programme. 

The first priority is to ensure that the instrumentation is operating correctly. Any controllers often out of service should be identified and the problems resolved. All control valves should be checked to ensure that they are correctly sized and the controller not liable to saturate. The type of valve (equal percentage or linear) should be checked. Calibration of valve positioners should be checked and any mechanical defect, such as excessive stiction or hysteresis, be rectified. Any excessively noisy measurements should be dealt with, if possible, by resolving the problem at source - rather than by the use of filtering. Resolution of some instrument problems can be delayed waiting for delivery of replacement parts or for a plant shutdown. It is therefore wise to identify any problems as soon as possible so that these are not on the critical path of the project. 

Reproducibility is expressed as the relative standard deviation (in %) of a check calibration standard and should be under 20%. The whole process has been repeated 10 times using water containing a low phthalate concentration. 

The reading on an instrument will be affected by imperfections in components in the instrument. If it is an electromechanical device, these errors will be due to magnetic hysteresis, friction, and tolerances on the sizes, assembly, and purity of the components. Likewise, for an electronic instrument, tolerances on components, assembly, and hysteresis of operation of the various circuits will affect the operation. In both types of instrument, ai r changes in the environment (temperature, humidity, and possibly pressure) will have an effect on the performance. Since many materials change their properties slightly with age (and continual use), it is necessary to consider the effect of age on the performance of an instrument. Since this is difficult to predict, it is essential that instruments be checked (calibrated) at regular intervals, for example, once a year, but preferably every 6 months. From the records (history) of instruments, confidence in the performance of a particular instrument is maintained. 

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