1. Influence of upstream and downstream straight pipe segments Because the calibration coefficient K value of the time-difference ultrasonic flowmeter is a function of Reynolds number, when the fluid transitions from laminar flow to turbulent flow, its velocity distribution is not uniform, and the calibration coefficient K value will have a great change, thus affecting the measurement accuracy.
2. The influence of the installation pipeline parameter Settings. According to the flow measurement formula qv= (π/4) D2v of the time-difference ultrasonic flowmeter, when the pipeline material and size Settings are inconsistent with the actual pipeline size, there will be errors between the theoretical pipeline flow cross-sectional area and the actual pipeline flow cross-sectional area, resulting in inaccurate calculation results.
3. The influence of the transducer installation, time difference method ultrasonic flowmeter measuring device transducer acoustic wave transmission is divided into linear type and reflection type, reflection type according to the installation mode and V, Z, W type, can be selected according to the diameter of the pipe, the nature of the measured flow body, whether there is pipe lining and site installation conditions. In addition, the transducer must be installed in the direction tangent to the pipeline, otherwise it will affect the transmission and reception of sound waves, and then affect the measurement accuracy of the ultrasonic flowmeter with the time difference method.
4. The influence of the measured flow body gas content, insoluble gas has very low acoustic impedance, may cause the sound beam dispersion, when the gas content is large, it will weaken the acoustic signal intensity, so the measured flow body gas content has a great impact on the ultrasonic flowmeter measurement data.
5. The influence of coupling agent, in order to ensure that the transducer can fully contact with the pipeline, the installation of the transducer needs to be evenly coated with a layer of coupling agent on the surface of the pipeline, the general thickness is 1mm, and the bubbles and particles in the coupling agent extrusion, the transmitter surface of the transducer should be closely attached to the tube wall.
6. The influence of temperature sensor. According to the working principle of ultrasonic calorimeter, the calorimeter is composed of a flowmeter, an integrator and a pair of temperature sensors. In order to ensure the measuring accuracy of the calorimeter, PT1000 with more precise index value is often used in the temperature sensor of ultrasonic calorimeter with time difference method, and it is configured in pairs. One installed on the supply pipe is marked red, and the other installed on the return water pipe is marked blue.
7. The influence of ultrasonic flowmeter installation position, ultrasonic flowmeter flow installation should be far away from high frequency interference sources, there should be a good grounding system, if necessary, can be set separately ground wire network. Power cables and signal cables shall be laid through metal pipes respectively, and the metal pipes shall be well grounded.
