Calibration method of insertion flow meter

The measuring head of the point flow type insertion flow sensor is essentially a flow velocity sensor, and its output signal is actually proportional to the flow velocity at the insertion point. Therefore, there are two calibration methods for point flow type insertion flow meters: the velocity meter method and the flow meter method.

1. Velocimeter method

The so-called velocity meter method is a method of calibrating only the measuring head of the point flow type insertion flow sensor and treating the measuring head as a velocity meter.

For frequency output type measuring heads (such as insertion turbine and insertion vortex flowmeters), the instrument coefficient of the measuring head is first measured on the calibration device, and then the velocity distribution coefficient is determined according to the fluid and pipeline conditions at the application site. The velocity

meter method has many advantages and should be the main method for calibrating point flow type insertion flow meters and should be widely promoted.

2. Velocimeter method calibration equipment and calibration method

The calibration method is: the flow meter measuring head is firmly fixed on the measuring vehicle, and the measuring vehicle moves on the tracks on both sides of the water tank.

The moving speed of the measuring vehicle represents the standard flow velocity of the water flow. The relationship between the flow velocity and the instrument signal is obtained by changing various vehicle speeds, thereby determining the velocity instrument coefficient of the measuring head.
If the flow meter manufacturer does not have a straight open slot and a low-speed wind tunnel, the circular tube flow standard device can also be used to calibrate the measuring head, but the velocity distribution coefficient and blockage coefficient of the test section of the circular tube flow standard device must be determined.

3. Flow meter method

The flow meter method is to calibrate the entire insertion flow sensor, including the measuring head, insertion rod, insertion mechanism, converter and measuring

pipeline, that is, the insertion flow meter is regarded as a full-tube flow meter and calibrated on the flow standard device to obtain the instrument coefficient. Therefore, its calibration equipment and method are exactly the same as those for calibrating a full-tube flow meter. It will not be introduced here.

4. Velocity meter method

The biggest advantage of the velocity meter method is that it only needs to calibrate the instrument coefficient of the measuring head, and the calibration equipment of the measuring head can be small and medium-sized, without the need to build a large flow standard device. Therefore, both the construction cost of the calibration device and the daily calibration cost of the instrument are relatively low. The insertion flow meter is the flow meter with the lowest production cost and operating cost among various large-caliber flow meters. Using the flow meter method to calibrate an insertion flow meter will make the production cost of the meter very high, and some large-diameter meters cannot even be calibrated at present. (end)