How the RTK Displacer Level Sensor works

STL Power & Process Controls has been the UK and Ireland RTK Channel Partner since 1998.

The RTK digital level sensor is the standard solution in industrial refrigeration and boiler water level control systems for accurately measuring liquid levels.  Suitable for use within a temperature range of -60°C to +280°C and nominal pressure PN40/PN100, these sensors are compatible with oils, all natural and synthetic refrigerants, and liquids with densities between 500-1500kg/m³.  The sensor can either be mounted outside a tank using a reference vessel or directly mounted if enclosed by a stilling tube.

The displacer level sensors use Archimedes’ Principle to detect the liquid level by continuously measuring the weight of the displacer rod immersed in the process liquid.  The displacer is cylindrical in shape with a long constant cross-sectional area. 

As liquid level increases, the displacer rod experiences a greater buoyant force, making It appear lighter to the sensing instrument, which interprets the loss of weight as an increase in level and transmits a proportional output signal.

As liquid level decreases, the buoyant force on the displacer rod decreases with a corresponding weight increase which is interpreted as decreasing level by the level sensor which then gives a corresponding signal output. 

The measured level is transmitted as a 4–20 mA signal, enabling easy integration with PLCs, controllers, or external displays.  In steam boilers, this is used for pump on/off, 1^st low water level, 2^nd low water level cut-out, high water level.

As standard, the sensor heads are equipped with an LED level indicator; a digital display on the sensor head is also available as an option. 

Features:

• Power supply: 24 V DC, output: 4–20 mA
• Linear measuring range: 150 to 4000 mm
• Wear resistance inductive tracing
• No connection between displacer and electronics
• All parts in contact with the medium are made of stainless steel
• Slim design
• Digital calibration
• LED display
• Connection thread – G1 or NPT
• Interchangeable head for ease of maintenance
• Versions for shock, vibration, or seismic test available on request
• Analogue technology suitable for nuclear plants

Application:

1. Level measuring with LED display per 10% steps and remote transmission with 4-20mA output
2. Level dependant pump regulation with switch-gear SG 2431/2411
3. Continuous level control with any controller and control valve

 For more information, please contact ash@stlpowerprocess.com

Search related valve / actuator articles:   STL Power & Process ControlsIssue 105Sensors