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Submersible Level Transmitters: Environmental Monitoring

Submersible level transmitters are primarily used for monitoring the levels of liquids, especially in environments that require precise measurement and monitoring. Here’s an expansion on environmental monitoring and the types of output signals, both analogue and digital.

Submersible level sensors and level transmitters

Environmental Monitoring

In environmental monitoring, submersible level transmitters are crucial for tracking water levels in various natural and man-made bodies of water, such as rivers, lakes, reservoirs, and groundwater wells. The applications include:

1. Flood Monitoring: They help in early detection of flood conditions by continuously monitoring river or lake levels.

2. Groundwater Monitoring: Understanding the groundwater level can aid in water management and conservation efforts.

3. Wastewater Treatment: In wastewater treatment plants, these sensors provide vital information needed for process control.

4. Tidal & Marine Monitoring: They are used to study the effect of tides and provide data for coastal management.

Types of Output Signals

The choice of output signals often depends on the specific application requirements, including accuracy, distance between sensor and control system, integration with existing systems, and cost.

Analogue Outputs

  1. 4-20 mA: A widely used current-based signal. It’s simple, reliable, and less affected by electrical noise, which makes it suitable for long-distance transmission.
  2. 0.5 to 4.5V / 5V supply: Often referred to as 10-90% output as it will ratiometrically adjust the output according to the supply voltage, these work from 3.3 to 5.5V dc and are ideally used for low power applications with short lengths of cable. Calibrated with the cable fitted to ensure cable resistance and voltage drop is catered for.

Digital Outputs

  1. RS485 Modbus: Allows for multidrop configurations and is typically used for more complex systems that require communication between multiple devices. Offers noise immunity and the ability to transmit over significant distances.
  2. SDI-12: Specifically designed for environmental data acquisition, SDI-12 provides a standard for digital data transmission. It allows for low power consumption, making it suitable for battery-powered remote monitoring systems.

Reasons for Choosing Certain Types of Outputs

1. Compatibility: The choice often depends on the existing systems and equipment to ensure seamless integration.
2. Distance: For long-distance transmission, RS485 Modbus might be preferred over analogue signals.
3. Accuracy and Resolution: Digital signals like RS485 Modbus can carry more information and provide higher accuracy and resolution.
4. Cost: Analog systems may be preferred for simple applications where cost is a factor.
5. Environmental Conditions: In highly noisy environments, digital signals are generally more immune to interference.


The application of submersible level transmitters in environmental monitoring is extensive, playing a crucial role in managing and protecting water resources. The choice of analogue or digital outputs will depend on the specific needs and constraints of the application, including compatibility, distance, accuracy, and cost considerations.