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1. The letters qb
appear before the displayed value of the electromagnetic flowmeter. The appearance of "QB" before the displayed value is usually a manufacturers custom code or specific operating condition identification, and in rare cases may be a signal of equipment failure. 1. In most cases, this is a normal phenomenon when the manufacturer customizes the code or functional mode. "QB" represents the device entering a specific working mode or displaying specific parameters. • Standard operating condition flow rate: commonly used in gas measurement, "QB" may represent "standard operating condition flow rate" (Qn), which is the flow rate value converted to standard temperature and pressure and displayed separately from the operating condition flow rate (operating condition m ³/h). • Batch control mode: In quantitative control systems, "QB" may represent "Quantity Batch" mode, which is performing quantitative filling/batch processing operations. • Manufacturer specific identification: For example, some models of Kaifeng Instrument Factory use "QB" to represent analog output status, while some models of KROHNE represent special calibration mode. 2 In rare cases, the abnormal status prompt of the device may be a fault code: • Sensor abnormality: electrode contamination, lining damage, or chaotic empty tube status, such as triggering the "QB" alarm with basic energy (please refer to the specific model manual for confirmation) • Signal interference: When strong electromagnetic interference causes signal distortion, abnormal codes may be displayed, and grounding and shielding treatment suggestions need to be checked. 1 Priority should be given to referring to the corresponding models instruction manual code table,
2. Description of the HART communication function of Kaifeng electromagnetic flowmeter
The HART communication function of Kaifeng electromagnetic flowmeter is implemented based on the HART bus protocol, and its core is to achieve bidirectional data transmission by superimposing digital frequency modulation signals on 4-20mA analog signals, supporting device parameter configuration, real-time diagnosis, and remote monitoring. The following is an explanation from three aspects: technical principles, functional characteristics, and usage precautions:
1. HART protocol technical principle signal superposition mechanism: The HART protocol adopts frequency shift keying (FSK) technology, which superimposes high-frequency digital signals on the habitual 4-20mA current loop. Logic "1" corresponds to a frequency of 1200Hz, logic "0" corresponds to a frequency of 2200Hz, and the baud rate is fixed at 1200bps. This design is compatible with existing analog systems while achieving digital communication functionality. A
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