Method for measuring the properties of liquid based on a quartz crystal microbalance sensor

A method for measuring the properties of liquid based on a quartz crystal microbalance sensor, the method comprising the following steps:

• (1). connecting a QCM sensor to a driving circuit, where the driving circuit is connected to a DC power, and the output of the driving circuit is connected to a frequency counter;
• recording the counting value displayed on the frequency counter, after the DC power is powered on, and the QCM sensor begins to work, where the counting value is the reference resonant frequency f0 of the QCM sensor;
• (2). loading a certain amount of sample liquid onto the QCM sensor's surface, where the volume of the sample liquid is VL1, and then, recording the counting value displayed on the frequency counter, where the counting value is the first resonant frequency f1 of the QCM sensor, and the first frequency shift is Δf1=f1−f0;
• (3). based on step (2), loading another certain amount of sample liquid onto the QCM sensor's surface, where the volume of the sample liquid is VL2, and then, recording the counting value displayed on the frequency counter, where the counting value is the second resonant frequency f2 of the QCM sensor, and the second frequency shift is Δf2=f2−f0;
• when the volume of sample liquid varies from VL1 to VL2, the difference between the second frequency shift and the first frequency shift of the QCM sensor is Δf2−Δf1;
• (4) the density of sample liquid ρL is calculated:
• ρ
• L
• =
• Δ
• 
• 
• f
• 2
• -
• Δ
• 
• 
• f
• 1
• K
• Pf
• ·
• C
• Pf
• ·
• V
• L
• 
• 
• 2
• ·
• f
• 0
• ;
• where CPf is a pressure-frequency constant, KPf is the pressure sensitivity coefficient of the QCM sensor, and obtained as follow:
• KPf=f0·Kf/nD;
• where n is the overtone number of the QCM sensor's electrode, D is the diameter of the QCM sensor's electrode, Kf is the force-frequency constant of the QCM sensor;
• (5). the viscosity of sample liquid ηL is calculated:
• η
• L
• =
• K
• Pf
• ·
• C
• Pf
• (
• Δ
• 
• 
• f
• 2
• -
• Δ
• 
• 
• f
• 1
• )
• ·
• V
• L
• 
• 
• 2
• ·
• f
• 0
• ·
• [
• Δ
• 
• 
• f
• 1
• ·
• V
• L
• 
• 
• 2
• -
• V
• L
• 
• 
• 1
• ·
• (
• Δ
• 
• 
• f
• 2
• -
• Δ
• 
• 
• f
• 1
• )
• K
• Tf
• ·
• C
• Lf
• ]
• 2
• ;
• where KTf is the stress sensitivity coefficient of the QCM sensor, CLf is the stress-frequency coefficient of the QCM sensor, and CLf is related to the properties of the sample liquid.