Prosonic 93 Low Flow Cutoff Setup Guide
The Prosonic 93 is an ultrasonic flowmeter commonly used in industrial sites. Its low flow cutoff function is used to suppress measurement fluctuations caused by tiny flows or bubbles in the pipeline, ensuring a stable output signal. Correctly setting the low flow cutoff is crucial for improving process control accuracy. This article introduces the setup method step by step and provides recommendations for key parameters.
1. Function and Principle of Low Flow Cutoff
Low Flow Cutoff means that when the flow rate is below the set threshold, the flowmeter forces the output to zero or holds the last valid value, avoiding false flow signals caused by fluid disturbance, bubbles, or noise. This function is especially suitable for batch processing and batching systems and other occasions with high requirements for zero-point stability.
1.1 Applicable Scenarios
- Suppress output fluctuation when the fluid in the pipeline is stationary or flowing very slowly
- Avoid instantaneous false flow accumulation during pump startup/shutdown
- Reduce noise interference for fluids containing bubbles or solid particles
1.2 Preparation Before Setup
- Confirm that the flowmeter has been installed correctly and zero calibration has been completed
- Understand the minimum flow value allowed by the process (usually 1% to 5% of full scale)
- Prepare a HART communicator or local operating interface (such as the Prosonic 93 display module)
2. Low Flow Cutoff Setup Steps
The following steps are applicable to the Prosonic 93 when setting via the local display or HART communication. The specific menu path may differ slightly depending on the firmware version; please refer to the actual instrument.
2.1 Enter the Setup Menu
- Press the E key to enter the main menu, and use the +/- keys to navigate to the "Setup" menu.
- Select "Process Parameter" → "Low Flow Cutoff".
- Press the E key to enter parameter editing mode.
2.2 Set the Cutoff Value
- Enter the required low flow cutoff value; the unit should be consistent with the current unit of the flowmeter (such as m³/h).
- It is recommended to set the initial value to 2% of full scale, then adjust according to on-site commissioning.
- Press the E key to confirm and save.
2.3 Verification and Commissioning
- Close the upstream valve and observe whether the flowmeter output stabilizes at 0.
- Slowly open the valve. When the flow exceeds the cutoff value, the output should smoothly follow the actual flow.
- If the output still fluctuates, the cutoff value can be appropriately increased, but it should not exceed 5% of full scale, so as not to affect low-flow measurement accuracy.
3. Key Parameters and Recommended Values
The table below lists recommended low flow cutoff values for different application scenarios for reference by engineering and technical personnel.
| Application Scenario | Recommended Cutoff Value (%FS) | Remarks |
|---|---|---|
| Clean water flow measurement | 1%~2% | Low noise; a smaller value can be set |
| Liquid containing bubbles | 3%~5% | Suppress bubble interference |
| Batch batching | 2%~3% | Balance accuracy and stability |
| Wastewater or slurry | 5%~10% | For high-noise occasions, it can be appropriately relaxed |
4. Precautions and Common Problems
4.1 Precautions
- The cutoff value should not be too large; otherwise, real low-flow signals will be lost and the totalized volume will be affected.
- After setup, the zero point must be verified again to ensure there is no offset.
- If the flowmeter is used for trade settlement, the cutoff value should comply with relevant metrology regulations.
4.2 Common Problems
- Problem: After setup, the flow display is always 0.
Solution: Check whether the cutoff value is greater than the actual flow and reduce it appropriately. - Problem: The output fluctuates greatly at low flow.
Solution: Increase the low flow cutoff value, or check whether the pipeline is full and whether there are bubbles. - Problem: Unable to enter the menu.
Solution: Confirm whether the instrument is unlocked; enter the password if necessary.
5. Summary
The low flow cutoff setup of the Prosonic 93 is a key step in ensuring flow measurement stability. By setting the cutoff value reasonably, noise and false flow can be effectively suppressed while real low-flow signals are retained. It is recommended to adjust within the range of 1%~10%FS according to actual working conditions and to follow the steps in this article for verification.