Daily application and signal processing of mass flow meter

Interest in mass flow meters has steadily increased over the past decade. Coriolis mass flow meter have been widely used in food, beverage, chemical, pharmaceutical, oil, natural gas and other industries. Along with people's attention, the performance of mass flow meter is also constantly developing. Its biggest advantage is that it can directly measure mass flow, while other instruments can only measure volume flow. The high precision, wide range and repeatability of the mass flowmeter are further reasons for its wide application and rapid development in the industrial field.

The driving circuit of the mass flowmeter must provide a precise driving pulse to make the tube vibrate at a precise amplitude. A rapid response is needed when the properties of the fluid change, such as air bubbles mixing into the fluid and increasing damping. This requires an increase in excitation energy to keep a steady oscillation amplitude. For this to be successful, the drive circuit should simultaneously control both oscillation amplitude and frequency to match with resonant frequencies of the system. This dynamic response performance is critical for certain applications which require quick control operations, periodic flow variations, or rapid batch irrigation.

The sensor obtains a weak sinusoidal signal, which requires amplification before further information processing. To minimize the zero point error, one should use an amplifier that owns a wide bandwidth. The amplitude ratio and time difference methods of phase difference measurement in the mass flow meter are typically achieved by analog circuits - which are known to be less stable and susceptible to various external factors like temperature - thus compromising accuracy. To overcome such issues, a Fourier transform algorithm aided by phase-locked loop technology is employed with dual-channel high-speed and high-precision A/D chips that sample both signals synchronously with DSP as the core for real-time calculation of phase differences and frequencies. This transition from analog to digital increases accuracy by suppressing any interference from higher order harmonics and noise. Overall, it enhances the precision of phase differences and frequency measurement resulting in increased accuracy of the mass flowmeter's outcomes.

Advantages of mass flow meters

1) Its anti-corrosion, anti-fouling, explosion-proof, wear-resistant and other problems have been satisfactorily solved, so it can measure a wide range of media, such as oil products, chemical media, papermaking black liquor, slurry, gas, fluids of solid particles and highly viscous objects.

2) There are no obstacles in the pipeline, no moving parts, less failure factors, and easy cleaning, maintenance and maintenance.

3) Easy to install, the inlet and outlet directions of sensor pipes of various sizes can be adjusted at will. Installation: adjustment, easy to use, no need to configure straight pipe sections for inlet and outlet.

4) It is easier to measure multiphase fluids.

5) Multi-parameter measurement, while measuring mass flow, volume flow, temperature and density can be obtained at the same time; it is not sensitive to influencing quantities, such as pressure, temperature, density and viscosity, and flow velocity distribution.

How to solve the problem of mass flow meter failure

Mass flowmeter is no stranger to us, and we have a certain understanding of its basic working principle and application fields. But what should we do if the coriolis type mass flow meter fails? In our general use process, we encounter the strike phenomenon of the flowmeter. Can we judge the failure of the flowmeter in time and find the corresponding solution. Below, I will give you a brief introduction to some common faults and corresponding solutions of mass flowmeters.

1. Mass flowmeter hardware failure:

If the error is too large, the display of the totalizer is not bright or does not add value, and the display is blank, the reasons are:

a. Irregular installation can directly lead to zero drift of the flowmeter. For example, the mass flow meter is installed close to the pump outlet, the sensor support strength is not enough, the connecting flange is improperly welded to generate stress signals, and the cable is subject to electromagnetic interference.

b. Wiring problem

If the display does not light up, check the power connection of the totalizer. If the fuse is burned, confirm whether the input voltage is consistent with the nominal value of the standard voltage, and whether the AC or DC form is consistent. And if the totalizer does not increase with the flow rate, check the wiring of the totalizer. If the totalizer is equipped with a forward/reverse program, check the wiring of the flowmeter. Does not increment when flowing.

c. Process medium change

If the measurement medium has air entrainment, gasification or two-phase flow, etc., the transmitter will display an alarm, and in severe cases, the sensor will stop working.

d. Transmitter failure.

e. Sensor failure.

f. Pipeline purging problem.

2. Mass flow meter software problem

Before installing and using the flowmeter that has just been calibrated, you must pay attention to the zero point calibration under the current working condition. You must ensure that the flowmeter is filled with medium and then close the stop valves at both ends to calibrate the zero point. There are many specific methods, panel operation , handheld device and use ProLink Ⅱ software.

a. The zero calibration is incorrect.

b. The parameter setting is wrong.

c. Pulse fluctuation of power supply.

d. I/O configuration is wrong (be sure to pay attention to the range).

e. The operation is wrong.