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Typical accuracy envelope of electromagnetic flowmeter

by:Sure     2021-08-04
8.2 Secondary device 8.2.1 Necessary data The following data should be printed on the nameplate: a) Meter type and serial number; b) Power supply: voltage, frequency and power; c) Output signal; d) Limit load impedance. 8.2.2 Optional data The following data can be optionally provided: a) Degree of protection of the enclosure. Note: If the size of the nameplate allows, such as trademarks, manufacturing date, etc. 8.2 Secondary device 8.2.1 Necessary data The following data should be printed on the nameplate: a) Instrument type and serial number; b) Power supply: voltage, frequency and Power; c) output signal; d) limit load impedance. 8.2.2 Optional data The following data can be optionally provided: a) Enclosure protection level. Note: If the size of the nameplate allows, additional explanations such as trademarks and manufacturing dates can also be included. 9 Calibration and test conditions 9.1 Wet calibration The calibration coefficients shall be determined by wet calibration with water on the test device under reference (nominal calibration) conditions (see 9.2). This condition for calibration should be such that the measurement can be traced back to a national or international reference. Therefore, the calibration is for a known uncertainty. For example, GB/T17612 and ISO8316 provide applicable calibration methods. GB/T18659 also gives an evaluation method for electromagnetic flowmeters. When the primary device is too large to be installed on the test device of the manufacturer, or the test device has insufficient flow, another larger flow test device can be used. If this is not possible, you can use the user's container or storage tank for on-site calibration, or use another reference flowmeter in the system for comparison. The total uncertainty shall be determined in accordance with the provisions in Chapter 10. The method usually called 'dry calibration' based on magnetic induction measurement and calculation of primary device signal based on physical size does not belong to the scope of this standard. 9.2 Nominal calibration conditions Nominal calibration conditions are those conditions that should be met during calibration. These nominal calibration conditions should be specified by the manufacturer. For the purpose of comparison. The flowmeter should be tested under the environmental range and flow conditions specified in GB/T18659. If the flowmeter has reached thermal equilibrium, when the influencing quantities remain within the working limit specified by the manufacturer, it is usually assumed that their influence on the metering characteristics of the flowmeter can be ignored. 9.3 Interpretation of results 9.3.1 Reference accuracy envelope The manufacturer shall provide the range of working conditions and their impact on performance. For details on the content of evaluating flowmeter performance, please refer to GB/T18659. The current practice is to specify a reference accuracy envelope for the specified flow range. A typical reference accuracy envelope is shown in Figure 7. 9.3.2 Accuracy under reference conditions Figure 7 Typical accuracy envelope. The accuracy of the flowmeter under reference conditions is determined by the combination of the flowmeter signal and volume flow measurement random and system uncertainty. of. Chapter 10 gives a summary of uncertainty analysis. The upper and lower limits of the uncertainty of each data point should be within the accuracy envelope (Figure 7) provided by the manufacturer. 9.3.3 Deviation from reference conditions Deviation from reference test conditions may affect flowmeter performance. Although these effects are usually compensated in the secondary device, the manufacturer should also specify an error limit for each influencing quantity. 9.4 Pressure test As required, the primary device or measuring tube shall be subjected to the test of the appropriate pressure specification standard. 10 Uncertainty analysis The calculation of the uncertainty of flow measurement should be carried out in accordance with the relevant national standards or ISO/TR5168. However, it is useful to review some of the basic principles and give the methods for applying these principles to electromagnetic flowmeter measurements. ISO/TR7066-1 and ISO7066-2 provide curve fitting for special calibration devices or data from user flow measurement devices
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