Gas flow measurement attention to several aspects of the description

1. When the working condition of the meter changes, the zero position of the meter should be re-adjusted. At the same time, the instrument's catheter must be installed horizontally and calibrated with a level. Otherwise it will increase the effect of changes in operating conditions on zero drift. The frame should not be shaken or rocked, so it should not be used on ships.
2. Although the specific heat of the real gas varies with the pressure and even the variation of some gases is relatively large, the measurement accuracy of the instrument can still maintain a certain range.

3. The choice of conduit material, in addition to considering corrosion resistance, is preferred to use materials with better thermal conductivity. Taking the nitrogen measurement as an example, it is also tested in the range of 0-100kg/cm2 pressure and 0-7 liter/hour flow rate. The measurement accuracy of the nickel tube is 2 to 2.5%, and the stainless steel is 3-4%. .
4. Correlate the large amount of test data in the range of 0-100kg/cm2 pressure and 0~7 liter/hour flow rate, and find the linear regression equation by the least squares principle. The correlation coefficient λ values are all in the range of 0.999～0.9999. , to prove that the instrument has a good linearity. However, the linearity and the range size have larger flow rates and the more nonlinear the nonlinearity, so the range is generally limited to 0 to 4 liters/hour to ensure good linearity. In order to measure large flow and ensure linearity, the shunting principle can be used to extend the range of the meter. If the bypass pipe, the venturi pipe, the orifice plate, etc. are used together, the range can be expanded to tens, hundreds, thousands of liters per hour, up to tens of thousands of standard cubic meters.
5. The meter must be warmed up before use, and the meter is unstable before it is fully warmed up. For a better model, the warm-up time is less than two hours.
6. During the use, when the gas flow suddenly changes, the heat is transferred and the temperature inside the tube is redistributed, so it takes a certain time for the output signal to re-stable. In order to reduce this hysteresis, manufacturers often add a differential network to the electrical lines of the instrument to allow the output signal to react quickly. This is especially necessary when working with other instruments to control traffic.
7. Since such meters must be operated normally when the specific heat of the gas is relatively stable, all the gas components are unstable, the center of the gas is fogged, and the working conditions are close to the liquefaction critical region of the gas, etc., because the specific heat value is very unstable, It is not advisable to use this instrument. If the critical point of liquefaction of ethylene is 50 kg/cm2, 9.9 °C, the meter reading will begin to destabilize when the pressure is more than 30 kg/cm2.