Portable open channel flowmeterWith the advantages of flexible mobility, convenient installation, and accurate measurement, it is widely used in scenarios such as agricultural irrigation, municipal drainage, environmental monitoring, and water conservancy surveys. It can quickly collect flow data for open channels (such as channels, waterways, and drainage ditches). This article will provide a detailed breakdown of its standardized operating procedures and scientific calibration methods to help users standardize the use of equipment and ensure the accuracy of measurement results.
1Portable open channel flowmeteroperating procedure
（1） Preparation before operation
Equipment inspection: Confirm that the flowmeter host, sensors (such as ultrasonic sensors, Doppler sensors), data cables, batteries (or chargers), brackets, and other accessories are complete and undamaged; Power on and check that the host has sufficient battery, and that the sensor probe is clean and unobstructed to avoid affecting signal transmission.
Site selection: Choose a measurement section with stable water flow, regular cross-section (rectangular, trapezoidal, U-shaped, etc.), no vortex, and no accumulation of debris in the open channel, and avoid areas with turbulent water flow such as bends, steep slopes, and near the outlet; Ensure that the depth of the measured water meets the equipment requirements (usually not less than 5cm), and that the sensor can fully cover the water flow cross-section after installation.
Parameter preset: Based on the type of open channel on site, basic parameters such as section shape (rectangular/trapezoidal/U-shaped), section size (width, depth, slope, etc.), measurement unit (m ³/h, L/s, etc.), measurement mode (continuous measurement/single measurement), etc. can be set on the host. Some equipment supports custom section parameters, which need to be accurately input according to the actual size.
（2） Equipment installation and debugging
Sensor installation: Fix the sensor above or on the side of the open channel through a bracket, ensuring that the probe is vertically aligned with the center of the water flow section and maintains a suitable distance from the water surface (usually 10-50cm according to the equipment manual), avoiding the probe from being immersed in water or blocked by floating objects on the water surface; If it is a contact sensor, it is necessary to ensure that the probe is in full contact with the water flow and does not affect the water flow state.
Signal debugging: After booting up, the host and sensor automatically pair (some devices require manual connection), and observe whether the signal strength and water level data displayed on the host are stable; If the signal is weak or the data fluctuates greatly, adjust the installation position and angle of the sensor, clean the surface stains of the probe until the signal is normal.
（3） Formal measurement operation
After confirming that the parameter settings are correct and the signal is stable, select "Start Measurement" on the host, and the device will automatically collect water level and flow rate data, and calculate the flow rate value based on the preset cross-sectional parameters.
During the measurement process, keep the site free of strong electromagnetic interference (such as staying away from high-power equipment and high-voltage lines), avoid personnel touching sensors or brackets, and prevent equipment displacement from affecting measurement accuracy; If the measurement mode is continuous measurement, the measurement interval can be set (such as 10 seconds/time, 1 minute/time) to automatically record multiple sets of data.
After the measurement is completed, select "Stop Measurement" and the host will automatically save the measurement data (some devices support USB export, Bluetooth transmission, or direct printing). Then turn off the host power, remove the sensor, and clean and store it.
2、 Calibration method for portable open channel flowmeter
The core purpose of calibration is to eliminate measurement errors caused by sensor wear, environmental interference, parameter drift, etc. during equipment use. It is recommended to calibrate every 3-6 months or before calibration in scenarios with high measurement accuracy requirements.
（1） Preparation before calibration
Prepare standard instruments such as standard measuring buckets, tape measures, stopwatches (suitable for volumetric calibration), or fixed open channel flow meters that have been verified and qualified (suitable for comparative calibration).
Select calibration environment: Conduct the calibration on an open channel section that is similar to the actual measurement scenario, ensuring smooth water flow, stable flow rate, no significant fluctuations, and known section dimensions (accurate measurement of width, depth, and other parameters).
Equipment inspection: Clean the sensor probe before calibration to ensure that the device has sufficient power and that the parameter settings are consistent with the calibration site.
（2） Common calibration methods
1. Volume method calibration (applicable to small and medium flow scenarios)
This is the most direct and accurate calibration method, which calculates the actual flow rate by measuring the volume of water flowing through it within a fixed time, and compares it with the measured value of the equipment for calibration.
Step 1: Install a shut-off device (such as a water baffle) downstream of the open channel to ensure that all water flow can be directed into the standard measuring bucket; If the flow is large, multiple measuring buckets can be used alternately to receive it.
Step 2: Measure the volume of the measuring bucket with a tape measure, or directly use a standard container with a volume scale; Record time with a stopwatch.
Step 3: Start the device for measurement, while opening the interception device to allow water to flow into the measuring bucket for a certain period of time (such as 30 seconds, 1 minute, the smaller the flow rate, the longer the time to reduce errors), then close the interception device and record the flow value displayed by the device (Q1).
Step 4: Calculate the actual flow rate Q2=V/T (V is the total volume of water in the measuring bucket, T is the receiving time).
Step 5: Compare Q1 and Q2. If the error exceeds ± 2% (the allowable error range specified by the equipment), enter the "Calibration Settings" interface of the host, adjust the coefficients (such as flow velocity coefficient and cross-sectional coefficient), and repeat the above steps until the error is within the allowable range.
2. Comparison method calibration (applicable to high flow scenarios)
When the flow rate is too high to use the volumetric method, calibration is performed by comparing with standard equipment.
Step 1: Install the portable open channel flowmeter and the legally certified fixed open channel flowmeter on the same open channel section, ensuring that their measurement areas are consistent.
Step 2: After the water flow stabilizes, start two devices simultaneously for continuous measurement and record multiple sets of data (at least 10 sets).
Step 3: Calculate the average of two sets of data to obtain the portable device average (Qping1) and the standard device average (Qping2), respectively.
Step 4: Calculate the error value=| Q flat 1-Q flat 2 |/Q flat 2 × 100%. If the error exceeds the allowable range, use the host calibration function to correct the parameters until the error meets the standard.
（3） Verification and recording after calibration
After calibration is completed, 1-2 sets of actual measurements need to be conducted again to confirm that the error between the measured values of the equipment and the actual values (or standard values) is stable within the allowable range.
Detailed record of calibration information, including calibration date, calibration environment (water temperature, flow rate, cross-sectional size), standard instrument information, error values before and after calibration, adjusted parameters, etc. Establish equipment calibration files for subsequent traceability and maintenance.
3、 Precautions for operation and calibration
Strictly follow the equipment manual to set parameters during operation, especially the precise measurement of cross-sectional dimensions, to avoid flow calculation deviation caused by parameter input errors.
The installation position of the sensor should avoid interference sources such as floating objects, aquatic plants, and mud on the water surface. During the measurement process, the cleanliness of the probe should be regularly checked.
Calibration shall be carried out under stable flow conditions to avoid calibration in extreme environments such as rainstorm and sudden rise and fall of water level, so as to ensure the effectiveness of calibration results.
If the device has not been used for a long time, it needs to be calibrated before being used again; If the error still cannot meet the standard after calibration, it may be due to sensor failure or damage to the host, and the manufacturer needs to be contacted for repair or replacement of parts.
By standardizing the above operational procedures and calibration methods, we can fully utilize themPortable open channel flowmeterThe flexibility advantage ensures the accuracy and reliability of measurement data, providing precise data support for water monitoring, environmental law enforcement, agricultural irrigation and other work.