Capacitive level transmitter is a liquid level measurement device commonly used in industrial fields. Its working principle mainly depends on the effect of the dielectric constant of the medium (such as liquid) on the capacitance. In short, when the liquid level meter probe is surrounded by liquid, its capacitance value will change due to the different dielectric constant of the liquid, so that the height of the liquid level can be measured indirectly.

First, we need to understand the concept of dielectric constant. Dielectric constant is a material property that indicates the degree of polarization of a medium to an electric field. For water, the dielectric constant is about 80; for air, the dielectric constant is about 1. The higher the dielectric constant, the greater the polarization of the electric field in the medium, resulting in a greater capacitance value in the capacitive level meter.

The main components of a capacitive level gauge include a capacitive sensor, a signal processing circuit and a display or output section. Capacitive sensors usually consist of a probe made of insulating material and a grounded metal container, forming a capacitor. When the level of a liquid rises or falls, the dielectric constant of the medium changes, thereby changing the capacitance value. The signal processing circuit converts this changing capacitance value into a height value of the liquid level, and finally provides it to the user through the display or output part.

Capacitance level gauges have certain requirements on the dielectric constant of the medium. The smaller the dielectric constant, the lower the accuracy and stability of the capacitive level meter measurement. The specific minimum dielectric constant value depends on the design and manufacturer of the capacitive level sensor. Generally, capacitance level meters can measure liquids with a dielectric constant greater than 1.5-2. However, this range is only a rough guide and the specific minimum dielectric constant value may vary from product to product.

To measure liquids with lower dielectric constants, it is recommended to refer to the equipment manufacturer's technical specifications or contact the manufacturer for more accurate information. At the same time, other types of level measurement technologies can also be considered, such as:

1. ultrasonic level gauge(ultrasonic level transmitter): Uses the reflection of sound waves on a liquid or solid surface to calculate the liquid level by measuring the time interval from emission to reception of the sound wave. Ultrasonic level gauges are not affected by dielectric constant and are therefore suitable for liquids with lower dielectric constants.

2. radar level gauge

(radar level transmitter): Calculate the liquid level by sending a microwave signal to the liquid surface and measuring the time interval of the microwave signal reflected from the liquid surface. Radar level gauges can be divided into two types: non-contact radar level gauges and guided wave radar level gauges.

2.1 Non-contact radar level transmitter: It uses radio wave (generally microwave) technology to produce reflections on liquid or solid surfaces. The non-contact radar level gauge does not directly contact the medium being measured, so it is less affected by factors such as dielectric constant, temperature, pressure, etc., and is suitable for liquids with lower dielectric constants.

2.2 Guided wave radar level transmitter: This type of radar level transmitter uses time domain reflection (TDR) technology to emit microwave signals along the measurement probe. When a microwave signal encounters a liquid surface, it reflects and travels back along the probe. By measuring the propagation time of the microwave signal, the liquid level height can be calculated. Guided wave radar level gauge has relatively low requirements on dielectric constant and is suitable for measuring liquids with low dielectric constant.

In addition to ultrasonic level gauges and radar level gauges, there are other liquid level measurement technologies, such as float level gauges, differential pressure level gauges, photoelectric level gauges, etc. Each liquid level measurement technology has its own characteristics and scope of application. Choosing a suitable liquid level meter requires comprehensive consideration based on various factors such as specific application scenarios, medium characteristics, measurement range, accuracy requirements, and environmental conditions. If you need to measure liquids with lower dielectric constants, you can give priority to ultrasonic level gauges and radar level gauges, which have less impact on the dielectric constant and are more suitable for this application scenario.