1、 The purpose of an open channel flowmeter is to be used in conjunction with a measuring weir to measure the flow rate of water in an open channel. Mainly used to measure the flow rate of sewage discharge outlets of sewage treatment plants, enterprise and government liquid units, and urban sewers. Due to the use of ultrasonic waves passing through the air, this instrument measures in a non-contact manner. Therefore, in the case of sticky and corrosive liquids, it has higher reliability than other forms of instruments. 2、 The working principle of open channel flowmeter is that the physical quantity directly measured by the open channel flowmeter is the liquid level. When used for measuring flow in open channels, a measuring weir groove is installed on the open channel. The measuring weir channel converts the flow rate in the open channel into the height of the liquid level. The instrument measures the water level in the measuring weir groove, and then calculates the flow rate based on the corresponding water level flow relationship of the measuring weir groove. The commonly used measuring weirs and channels include right angled triangular weirs, rectangular weirs, and Bacher channels (Figure 3). When using an ultrasonic open channel flowmeter, it is necessary to know the corresponding relationship between the water level and flow rate of the dosing weir tank during installation. The water level flow relationship of the measuring weir can be found in the national metrological verification regulation "Open Channel Weir Flow Meter" JJG711-90. Once the Bacher trough knows the throat width b, it can use the corresponding formula to calculate the relationship between water level and flow rate. There are corresponding formulas for right angled triangular weirs and rectangular weirs. But it also depends on the size of the installation channel. When determining the water level flow relationship, the triangular weir is related to the channel width B, opening angle, and upstream weir height p. The rectangular weir is related to the channel width B, opening width b, and upstream weir height p. Principle of Ultrasonic Liquid Level Measurement: This instrument uses ultrasonic echo ranging method to measure liquid level. The probe is fixedly installed above the water level observation point of the measuring weir. Aim the probe at the water surface. The probe emits ultrasonic waves towards the water surface. The working principle of the instrument: The instrument controls the probe to emit and receive ultrasonic waves. Measure the transmission time of sound waves to calculate the liquid level in mm. By checking the water level flow meter, convert the liquid level into flow rate (unit: liters/second). Instrument display: The instrument displays the liquid level height, instantaneous flow rate, and accumulates the instantaneous flow rate over time to obtain the cumulative flow rate. The instrument output includes 4-20mA current analog quantity; The switch quantity of the relay (to be ordered and selected); RS485 digital signal; What are the technical parameters of the Bacher trough open channel flowmeter? Flow range: 0.1 liters per second to 10 cubic meters per second? Traffic uncertainty: 5% 3)? Static pressure ranging: 2.4 meters? Probe blind spot: 0.4 meters (cannot be used for measurement within 0.4 meters from the flange of the probe) 5)? Distance measurement error:<0.4%? Or ± 3 millimeters (within 1 meter range) 6)? Water level resolution: 1mm7)? Accuracy: Level 0.5 (8)? Medium temperature: 0-60 ℃ 9)? Pressure flow, free flow 10)? Channel type: Channel type 11)? Protection level: IP6512)? Power supply: 220VAC 50HZ13)? Connection method: flange 14)? Instrument display: displays instantaneous flow, cumulative flow, and historical records of more than 4 years. Power consumption: ≤ 15W15)? Power supply voltage? : 24VDC ± 10% or 12VDC ± 10% (24VDC is recommended for 4-20mA) 16)? Customization of other power supply voltages (17)? Losing???? Out? RS485, M-BUS (capable of meter reading with centralized M-BUS collectors such as electric meters), 4-20mA output, 18)? Transmission protocol? MODBUS protocol, Nine Wave protocol 19)? Range and zero position: digitally adjustable 20)? Start time? Within 2 seconds (21)? Environmental temperature? 0 to 70 ℃ (22)? Display method? LED or LCD display (with backlight) 23)? ambient humidity? 5% -95%, no condensation, 24)? Zhen???? Moving? ：≤10g，f≤55Hz， Amplitude ≤ 0.5mm25)? Take it???? The ground? In areas with high electromagnetic interference, the transmitter and cable shielding layer should be well grounded? Fine???? Degree? ：±0.2％，±0.5％27)? Line???? Sex? ：±0.2% ，±0.5％28)? Electrical interface? ：M20×1.529)? Can the sensor heating device be selected according to the environment (30)? Expansion port: external Doppler ADCP adaptive port (I) JZYBS-D51B-2 standard Bacher slot installation

(1) Preparation for civil engineering installation of open channels: Before installation, the terrain must be inspected first, and the inlet must be higher than the outlet to ensure a water level difference and smooth outlet. This is the key to successfully installing the Bacher trough open channel flowmeter. Figure 3-35 Simulation diagram of Bacher metering tank (2) Requirements for placing the Bacher tank into an open channel: ① There is a water level difference at the downstream discharge outlet of the Bacher tank, and the discharge is smooth. If the water level difference is not enough, the Bacher tank should be raised to increase the water level difference. ② Ensure that the straight section in front of the Bacher groove has an installation distance of 3-5 times that of the groove body. (3) Reinforce the Bacher trough by pouring concrete on both sides to ensure that all water flows through the Bacher trough. During reinforcement, the Bacher groove should be kept horizontal on both sides to prevent tilting and deformation. When reinforcing, the centerline of the water flow in the Bachel trough must coincide with the centerline of the weir trough. (4) After the installation of the Bacher slot for instrument wiring, wait for the concrete to solidify before proceeding with instrument installation and debugging. Generally, installation and debugging should be carried out by instrument technicians. If the signal transmission cable of the split is far away, users can extend it themselves, and the distance is generally within 20 meters. Otherwise, field connection experiments should be conducted.

1. Install a measuring weir and use this instrument to measure flow. A measuring weir must be installed on an open channel. The construction and installation methods of the measuring weir groove can be found in Chapter 7 "Technical Reference for the Construction and Installation of Measuring Weir Groove" of this manual.

2. The probe should be installed on the probe bracket. The product is not equipped with a bracket at the factory, and the installation position of the probe on the channel should meet the requirements of the measuring weir according to the construction conditions of the measuring tank used on site. Generally, triangular weirs and rectangular weirs should be installed upstream of the weir plate, with a distance from the weir plate equivalent to 3 to 4 times the water depth passing through the weir (the water depth passing through the weir refers to the flow rate exactly equal to the zero liquid level)

This instrument uses ultrasonic echo ranging method to measure liquid level. The probe is fixedly installed above the water level observation point of the measuring weir (the location of the water level observation point can be found in the weir structure description). Aim the probe at the water surface. The probe emits ultrasonic waves towards the water surface. The ultrasound passes through t1 time, travels E1 distance, and touches the calibration rod. A portion of the ultrasonic energy is reflected by the calibration rod and received by the probe. The instrument records the length of time t1 during this period. Another part of the ultrasonic energy bypasses the calibration rod and reaches the water surface after t2. This part of the energy is reflected by the water surface and received by the probe. The instrument records the length t2 of this period. The calibration rod has been fixed on the probe. The length E1 of the calibration rod will not change. The instrument calculates the distance D from the water surface to the probe based on the ratio of t1 to t2, multiplied by E1. D=E1 ╳ t2/t1. When installing the instrument, set the distance L from the probe to "water level=0" in the instrument memory by pressing the button. The instrument reads the parameter L from the memory, subtracts D from L, and calculates the liquid level H (H=L-D). Due to the inconsistent length of E1 in product production; The delay of the circuit is also inconsistent. The calculation formula used for the actual liquid level of the instrument is H=L-KD, where "K" is the linear correction coefficient. The value of "K" needs to be calibrated to determine.