
Capacitive Level Transmitters

Capacitive level transmitters are devices used for level measurement of both liquid and solid materials. The technology behind these transmitters is based on the principle of capacitance.
A capacitor typically consists of two electrodes or plates separated by a non-conductive substance, or dielectric. In the case of capacitive level transmitters, the sensor often forms one plate of the capacitor, while the tank or vessel wall forms the other. The dielectric is the material being measured (e.g., a liquid or bulk solid) within the vessel.
The capacitance of this setup is directly influenced by the amount of material in the vessel. As the level of the material rises or falls, the dielectric constant of the capacitor changes, which in turn alters the capacitance. This change in capacitance is measured and converted into a level reading.
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More Information about Capacitive Level Transmitters
Capacitive level transmitters can work effectively across a broad range of conditions, including high temperature environments and with materials that have low dielectric constants. The absence of moving parts contributes to their reliability and long lifespan.
Some capacitive level transmitters are capable of continuous level measurement, while others are configured for point level detection. Point level capacitive sensors trigger an action when the material reaches a specific level, whereas continuous level sensors provide real-time monitoring of the level of material in the tank.
Capacitive level sensors are available in conductive and non-conductive versions. Conductive capacitive sensors can detect the presence of conductive liquids, whereas non-conductive capacitive sensors are suitable for non-conductive liquids and bulk solids.
In an empty tank, the capacitance is at its minimum. As the tank fills, the capacitance increases due to the higher dielectric constant of the liquid or solid compared to air. The measured increase in capacitance is directly proportional to the level of the material in the tank.
FAQs
Do capacitance level sensors provide capacitive level measurement?
Yes, capacitance level sensors indeed provide capacitive level measurement. The main operating principle of a capacitance level sensor involves the capacitance change that is produced by the change in the level of a substance.
Transmitters vs Transducers
Some of the most common types of transmitters and transducers can be found on pressure instruments. Examples of these include: drop-in well pressure devices and devices that measure the pressure in a pipe or gas chamber. Transmitters and transducers can also be found on flow and speed measurement devices.
What is the difference between transmitters and transducers?
The main difference is the way they send data to the monitoring device, like a PLC. In terms of measurement, the transmitter will reference a measuring unit by sending a milliamp signal (such as 4-20 mA). A transducer will reference a measuring unit by sending a voltage signal, typically in volts or millivolts.
Why have the two different types of transmission methods?
The method will depend on the application. If the electrical connection in the application travels a short distance, a pressure transducer is the better choice. Pressure transducers are smaller with fewer active electronic components that can be upset by electromagnetic interference. Also, the voltage signals transmitted over longer distances are subject to voltage drop and signal corruption. A transmitter is better for transmitting signals over a long distance.