Prowirl 72/73 Low Flow Cutoff Configuration Guide
What Is Low Flow Cutoff?
Low flow cutoff is an important function in vortex flowmeters used to eliminate nonlinear measurement errors. When the fluid flow rate is below a certain value, the output signal of the vortex flowmeter becomes unstable, resulting in decreased measurement accuracy. By setting a low flow cutoff value, the initial nonlinear range in the measurement span can be effectively removed, ensuring that the flowmeter operates within the effective linear range.
Principles for Determining the Low Flow Cutoff Value
The activation value of the low flow cutoff function can usually be set to the flow rate corresponding to a fluid Reynolds number = 20,000. The core purpose of this principle is to completely remove the initial nonlinear range in the measurement span, ensuring that the flowmeter always operates within a stable linear region.
The fluid flow rate and Reynolds number can be calculated using E+H's "APPLICATOR" software. This software is specifically designed for flowmeter selection and calculation. Before instrument installation, it can calculate the data that needs to be set, providing accurate reference information for engineering and technical personnel.
Using the APPLICATOR Software
The "APPLICATOR" software can be downloaded from the Internet at: www.applicator.com. Through this software, users can:
- Calculate the fluid Reynolds number under specific operating conditions
- Determine the flow rate value corresponding to a Reynolds number of 20,000 at minimum flow
- Obtain the recommended low flow cutoff setting value
- Perform flowmeter selection calculations
It is recommended to use the APPLICATOR software for calculations before instrument installation so that the parameters to be set can be determined in advance.
Setting Range for the Low Flow Cutoff Value
Generally, the low flow cutoff is already set at the factory. The low flow cutoff value of the parameter ON-VAL.LF-CUTOFF is generally 1% to 5% of the operating span, and the specific value needs to be cut off according to actual application requirements.
| Parameter Item | Description | Recommended Value |
|---|---|---|
| Reynolds Number Reference | Minimum Reynolds number to ensure linear measurement | 20,000 |
| ON-VAL.LF-CUTOFF | Low flow cutoff value (percentage of operating span) | 1% to 5% |
| Calculation Tool | E+H APPLICATOR software | www.applicator.com |
Configuration Steps
- Use the APPLICATOR software to calculate the Reynolds number under the operating conditions and determine the flow rate value corresponding to a Reynolds number of 20,000.
- Based on the calculation results, determine the low flow cutoff value (usually 1% to 5% of the operating span).
- Enter the parameter setting menu of the Prowirl 72/73 and locate the ON-VAL.LF-CUTOFF parameter.
- Enter the calculated low flow cutoff value.
- Save the settings and exit the menu.
Notes
- The low flow cutoff is usually preset at the factory. If modification is required, please refer to the actual operating conditions.
- If the cutoff value is too small, it may cause nonlinear errors; if it is too large, it may lose the effective measurement range.
- It is recommended to use the APPLICATOR software for precise calculation and avoid setting based on experience.
- For different fluids and piping conditions, the flow rate value corresponding to a Reynolds number of 20,000 is different and must be calculated separately.
Correctly setting the low flow cutoff function can significantly improve the measurement accuracy and stability of the Prowirl 72/73 vortex flowmeter in the low flow region, and it is a key step that cannot be ignored in engineering commissioning and procurement selection.