In the technical parameters of ultrasonic flowmeters, reading accuracy and full-scale accuracy are two core concepts describing measurement precision, with distinct definitions, application scenarios, and influencing factors. Here is a detailed explanation:
1. Reading Accuracy
Definition
Reading accuracy refers to the error between the flowmeter’s measured value and the actual flow rate, expressed as a percentage of the actual measured value. Its calculation formula is:
Error = ± (a% × Actual measured value + Fixed deviation)
Where
Error = ± (a% × Actual measured value + Fixed deviation)
Where
a% is the percentage of reading accuracy, and the fixed deviation is usually a compensation value for low flow rates (e.g., ±0.01 m³/h).Characteristics
- Error is proportional to the actual flow rate: The larger the flow rate, the greater the allowable absolute error; the smaller the flow rate, the smaller the allowable absolute error.
- More aligned with real-world usage scenarios: In situations with significant flow fluctuations (e.g., industrial pipelines where flow may vary from low to high), reading accuracy better reflects measurement precision.
- Example: If a flowmeter has a reading accuracy of ±1%, when the actual flow rate is 100 m³/h, the allowable error of the measured value is ±1 m³/h (i.e., 99–101 m³/h); when the actual flow rate is 10 m³/h, the allowable error is ±0.1 m³/h (i.e., 9.9–10.1 m³/h).
2. Full-Scale Accuracy
Definition
Full-scale accuracy refers to the error between the flowmeter’s measured value and the actual flow rate, expressed as a percentage of the flowmeter’s full-scale range. Its calculation formula is:
Error = ± (b% × Full-scale value + Fixed deviation)
Where
Error = ± (b% × Full-scale value + Fixed deviation)
Where
b% is the percentage of full-scale accuracy, and the full-scale value is the maximum flow rate the meter can measure (e.g., 1000 m³/h).Characteristics
- Error is fixed relative to the full-scale range: Regardless of the actual flow rate, the error range is determined by the full-scale value, independent of the actual measured value.
- Potentially large errors at low flow rates: If the actual flow rate is much lower than the full scale, the relative error increases significantly.
- Example: If a flowmeter has a full scale of 1000 m³/h and an accuracy of ±1%, the allowable absolute error is ±10 m³/h whether the actual flow rate is 1000 m³/h or 100 m³/h. In this case, when the actual flow rate is 100 m³/h, the relative error could reach ±10%, much higher than the performance of reading accuracy.
3. Key Differences and Application Scenarios
| Comparison Dimension | Reading Accuracy | Full-Scale Accuracy |
|---|---|---|
| Error Reference | Percentage of the actual measured value | Percentage of the full-scale value |
| Low-Flow Performance | Small errors, high relative precision | Large errors, low relative precision |
| Application Scenarios | Scenarios with large flow fluctuations or high demand for low-flow accuracy (e.g., municipal water supply, energy metering) | Scenarios with stable flow near full scale (e.g., fixed industrial pipelines) |
| Advantages | Better reflects real-world precision needs | Technically simpler to implement, potentially lower cost |
4. Summary
- Reading accuracy better reflects a flowmeter’s true measurement capability across the full range, especially suitable for scenarios with large flow variations. It is a key indicator for high-precision flowmeters.
- Full-scale accuracy performs well when flow is near full scale but may have large errors at low flow rates, typically used in scenarios with low precision requirements or stable flow.
When selecting an ultrasonic flowmeter, prioritize devices specified with reading accuracy (especially in scenarios where low flow rates are common) based on actual flow ranges, precision requirements, and application scenarios to ensure measurement accuracy.
Post time: Jul-22-2025