Level Switch Vs Level Transmitter | What is the Differences

Brian Craig

December 26, 2019

Level sensing is an important requirement in industries that utilize different types of fluids for functioning. The increase or decrease in the levels of a fluid may alter the results of the end process, or may also adversely affect people and environment around. To avoid this, industry users rely on various types of level sensing devices such as level switches and level transmitters. These devices help users measure the level of fluids accurately and avoid untoward incidents. Although the aforementioned devices are designed to measure the levels of fluids in various applications, they differ in terms of their operation. What is the difference between a level switch and a level transmitter? How to choose the right device for your application? Read the post to find answers.

Understanding Level Switches and Level Transmitters

What is a Level Switch?

A level switch is a point-level detection device that monitors high or low levels of fluids or solids in a tank or vessel. When the level reaches a preset point, it triggers an alarm or activates equipment (like pumps or valves). These switches are ideal for preventing overflow, dry-run conditions, or low-level alarms in tanks.

What is a Level Transmitter?

A level transmitter is a continuous measurement device that monitors material levels in real-time. It provides a variable output signal, such as 4–20 mA or digital protocols like HART, allowing for precise level control and integration with SCADA or PLC systems. These are preferred in processes that require accurate monitoring of liquid or solid levels over time.

Working Principle of a Level Switch and a Level Transmitter

The function of a level switch and level transmitter can be understood by their working principle.

The working principle of a level switch is easy to understand because it works like any alarm switch that turns on/off when the level of fluid goes above or below the predetermined level. When there is variation in the level, the device produces a sound or raises an alarm in some other way. The device works to activate the desired response from a user. The output of a level switch may or may not be voltage-dependent. At times, it may have a voltage-free contact, or sometimes it may have a fixed voltage 0-12 voltage.
The level transmitter is set with a variable output signal of 4-20 mA. For instance, the level transmitter for a 20-meter high tank will read 20 mA for a full tank, 4 mA for an empty tank, and 10 mA for a half tank. These devices may perform the level measurement in point values or continuously.

Level Switch Vs Level Transmitter – Important Factors to Consider During Selection

Do you think knowing the level switch and level transmitter working principle is enough to make the right selection? No, you need to understand different aspects related to them. The following factors will help you understand it better:

Measurement: A level transmitter is perfect for a condition where the exact level of fluid needs to be measured. This is usually preferred for applications where precise measurement becomes a necessity. A level switch is an ideal choice for applications where extreme low or high levels need to be measured. These devices help prevent leaks, overfills, and dry situations.

Level switches and level transmitters are distinguished into two categories – point level switches and continuous level transmitters. Some examples of point level switches include optical liquid level switches, horizontal float switches, vertical level switches, and ultrasonic level sensors. Submersible level sensors, ultrasonic level sensors, and capacitive level sensors are a few examples of continuous level sensors.

Understand Environmental Factors: The choice of a level transmitter or a level switch will depend on various environmental factors such as:

Pressure and temperature: Effects of temperature and pressure on transmitters or level switches may vary if the material undergoes a transition from one state to another. These devices are available in different materials and designs. So, you need to understand the temperature and pressure impact on a particular material, before selecting them for your application.
Range of measurement: Continuous level transmitters are used for level sensing dry or liquid materials within a specified range. They measure over a large range of levels which helps the user understand the right amount of substance. Most continuous level transmitters produce an analog output to indicate the level of fluid in the container. Against this, level switches are suited for point measurements.
Type of output: Level switches and transmitters are suited for producing different types of outputs – relay, analog, and digital.
Chemical compatibility: These level sensing devices may be used with a variety of liquid media. At times, the housing of the transmitter may come in contact with the media, which may affect its integrity. It is important to address the concern of the impact of different chemical media on sensors.
Tank size and shape: The choice of level sensing device may also depend on the tank size and shape. Extra narrow or wide tanks may have specific requirements.

A fair consideration of these factors will aid you in making the right selection. Even if you have an understanding and knowledge of these factors and your application requirements, it is still recommended to partner with a trusted supplier like The Transmitter Shop. The company provides various types of new and reconditioned transmitters.

Frequently Asked Questions (FAQ):

What is a level transmitter?

A level transmitter is a device that continuously measures and monitors the level of liquids or solids in a tank or vessel, providing real-time output for process control.

What is the difference between a level switch and a level transmitter?

A level switch provides on/off status at a specific level, while a level transmitter provides continuous, analog or digital level measurement across the full tank height.

What is the difference between a level switch and a flow switch?

A level switch detects fluid level at a specific height in a container, whereas a flow switch detects whether a fluid is moving through a pipe or not.

Which industries commonly use level transmitters and switches?

Industries like chemical processing, oil & gas, water treatment, pharmaceuticals, food & beverage, and power generation rely on both level transmitters and level switches for accurate and reliable fluid control.