How to select the flow sensor

Liquid density sensor means can feel liquid density , and it can be converted into an output signal that can be used sensors, liquid density sensor can be divided into six categories: capacitive, ultrasonic , tuning fork , resonant , radiation type and vibrating tube liquid Shaft Position Sensor . Capacitive liquid density sensors it is not based on the same liquid sample , the standard different buoyancy body , this will lead to an object connected with standard two capacitance change in the distance between the plates , and resultant capacitance changed. Because different liquid density sensor for different occasions , so in practical application , it should be depending on the nature of the liquid to be measured also on the measurement accuracy requirements, and so the situation and the choice of suitable sensors. Ultrasonic Density sensors it is higher than the frequency of the ultrasonic mechanical waves of 20kHz and an ultrasonic wave only may be in the form of propagation in a liquid medium . It is for the phase , frequency, speed and attenuation properties of the medium will be subject to impact , so, it can be based on the ultrasonic propagation properties and some of the correspondence between the density of the liquid to measure the density of the liquid . Its main advantages are: it can achieve non-contact measurement, the measurement accuracy is relatively high, relatively fast response ; and it has no moving parts , so the stability of the measurement is better ; it is not radioactive , there is no harm to the human body . The disadvantage is that there are impurities in the liquid medium , for example , bubble can lead to severe attenuation of the ultrasonic signal ; precision measurements in viscous media , the need to consider the impact of medium viscosity ; it will make some measurements lead to instability .Auto Temperature Sensor it is based on the liquid density in the liquid , the mass of small tuning fork vibrates, its inherent frequency change , so to measure the density of the liquid . To obtain high accuracy measurement results , it is necessary to detect the resonant frequency when the change is small , it is necessary to design rational vibrating unit , so that the vibration unit can be a relatively high mechanical quality factor . Fork usually made ​​of glass or stainless steel . Resonant resonant liquid density sensor measuring principle is based on the vibration characteristics of a harmonic oscillator to work . In operation, the resonator can be equivalently used as a single degree of freedom system , with the natural frequency of the vibration , the natural frequency of the system with the system is only the equivalent elastic modulus and the equivalent mass . Resonant liquid density sensor measuring principle is the liquid through the system and the elastic contact with sensitive components cause changes in the system of equivalent mass , resulting in changes in the natural frequency of the system . Measuring system according to a fixed frequency variation can know the density of the liquid to be measured . Liquid Density Sensor ray rays Liquid Density Sensor The main disadvantages are: it is not very high resolution ; it needs a relatively long time have stability ; It requires radioactive ray source . Its advantages are: the liquid flow sensor does not generate resistance to the flow size is not limited, and it can measure the density of the multiphase fluid ; when it is not in contact with the measurement of the liquid under test , it can be realized non-contact measurement . Liquid Cooling Temperature Sensor vibrating tube vibrating tube type liquid density sensor can reasonably be arranged drive member , to allow the inside tube vibration in the same plane , it is the measured density of the liquid flowing in the tube the average mass density . The sensitive element is that it uses a long tube vibration , its length is about 20 times the diameter .