Measurement principle and error analysis of surface tensiometer

Surface tension is a physical property of liquid surface, which reflects the strength of interaction between liquid molecules. Measuring surface tension is of great significance for understanding the physical properties and chemical reaction process of liquids. Surface tensiometer is an instrument specially used to measure the surface tension of liquid, and its measuring principle is mainly based on force balance and sensor technology. However, in actual measurement, due to the influence of various factors, the measurement results often have certain errors. This paper will introduce the measurement principle in detail and analyze the factors that may lead to errors.

First, the measurement principle

The measuring principle of surface tensiometer is usually based on large bubble method or suspension drop method. The bubble method indirectly calculates the surface tension by forming a gradually increasing bubble on the liquid surface and measuring the large pressure difference at the moment when the bubble bursts. The rule of hanging droplets is to hang a gradually increasing droplet on the liquid surface and measure the shape and weight of the droplet when it reaches equilibrium, so as to calculate the surface tension.

In the larger bubble method, the bubbles are gradually enlarged by accurately controlling the gas flow rate and pressure, and the pressure difference on the bubble surface is measured at the same time. When the bubble reaches the critical size, the surface tension and gas pressure reach equilibrium, and the pressure difference measured at this time is the function of surface tension. Through the known formula, the pressure difference can be converted into a specific value of surface tension.

In the suspended droplet method, high-precision camera and image processing technology are usually used to capture the shape change of droplets. When the droplet reaches the equilibrium state, its shape follows certain geometric laws. By measuring the radius of the base circle and the height of the droplet, the surface tension of the droplet can be calculated.

Second, the error analysis

Although the measurement principle is relatively simple, in practice, due to the influence of various factors, the measurement results often have certain errors. The following are the main factors leading to the error:

1. Environmental factors: Environmental factors such as temperature, humidity and air pressure have significant influence on the measurement of surface tension. For example, a small change in temperature may lead to a significant change in the surface tension of a liquid. Therefore, maintaining the stability of the measurement environment is the key to reduce the error.

2. Instrument accuracy: Accuracy directly affects the accuracy of measurement results. Factors such as sensor sensitivity, resolution and calibration accuracy may cause errors. Therefore, it is very important to select high-quality and strictly calibrated instruments to reduce errors.

3. Operation skills: The proficiency and operation skills of the operators will also have an impact on the measurement results. For example, in the larger bubble method, it requires the experience and skill of operators to control the stability of gas flow rate and pressure. In the suspended droplet method, it is also the key to accurately capture the equilibrium state of droplets and accurately measure their shapes.

4. Sample treatment: the treatment method and state of the sample will also have an impact on the measurement results. For example, the temperature, concentration and surface cleanliness of the sample may affect the measurement results of surface tension.

In order to reduce the error, besides selecting suitable instruments and operating environment, a series of measures should be taken, such as calibrating and maintaining instruments regularly, training operators to improve their skills, and optimizing sample processing methods. In addition, through in-depth analysis and research on the error source, it can provide strong support for further improving the accuracy and reliability of surface tension measurement.

In a word, surface tensiometer is an important tool to measure the surface tension of liquid, and its measuring principle is based on mechanical balance and sensor technology. However, in practical application, due to the influence of various factors, the measurement results often have certain errors. Therefore, we need to deeply understand the source of error and take corresponding measures to reduce the error, so as to improve the accuracy and reliability of surface tension measurement.