Although the use of ultrasonic open channel flowmeters has brought great convenience to the measurement of sewage flow, due to the inherent weaknesses of ultrasonic and electronic measuring instruments, such as susceptibility to temperature, radiation, etc., if it cannot be installed and used correctly, it will It seriously affects the measurement accuracy and the service life of the instrument, so the following points should be paid attention to during the installation and use of the ultrasonic open channel flowmeter.
1. The installation of weirs and troughs should be standardized
Ultrasonic open channel flowmeters must use water measuring weir grooves when measuring. After the water measuring weir grooves are installed on the open channel, the corresponding relationship between flow and liquid level must be established in accordance with the specifications. According to the flow pattern of the water in the channel and the size of the flow in the channel, the type of weir and trough is selected: when the flow of the measured water flow is less than 40L/s, the right-angled triangular weir is used; when the flow of the water is greater than 40L/s, the bar is used. Sheer trough; when the water flow is greater than 40L/s and the water level drop of the open channel is large, a rectangular weir is used.
2. Ultrasonic probe is set as required
Ultrasonic probes should be set up in accordance with the specifications when installing in open channels. Before installing the probe, be sure to install the probe and the bracket firmly without any looseness. Once the probe becomes loose after installation, the reference point on the water surface will change, which will affect the accuracy of the measurement. When installing the probe, it should be kept perpendicular to the horizontal plane without tilting; when measuring the water volume, the position of the triangular weir and the rectangular weir must be installed upstream of the weir plate, and the distance from the position of the weir plate is approximately equal to the maximum water depth (maximum overpass). Water depth of the weir: 3 to 4 times the value of the water flow level when the flow is the maximum; the installation position of the Parshall trough is at the position of 1/3 of the inlet contraction section.
3. Installation of the main unit of the meter and its water level check
The main unit of the meter should be installed in a room with no corrosive gas and well ventilated. When it must be installed outdoors due to special circumstances, the meter box should be protected. When using the instrument for the first time, you need to input the actual parameters of the project into the host, confirm the probe model, set the sound velocity, signal type, and the corresponding weir and trough type, and set the water level and flow meter of the instrument correctly. When the measuring instrument is installed and overhauled for the first time, if the probe needs to be moved, the liquid level of the instrument must be approved first. The actual liquid level and the zero point should be set during liquid level calibration: use measuring tools such as rulers and rangefinders that meet the accuracy requirements, fill the weir trough with an appropriate amount of water, and calibrate whether the indicated value of the meter is equal to The liquid level of the weir tank; when the water level in the equivalent water weir tank is zero, the liquid level of the meter is also zero; the purpose of the liquid level calibration is to ensure the actual water level in the weir tank and the instrument measurement The liquid level value remains the same.
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