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Liquid and Fluid Level Sensors and Gauging

Liquid And Fluid Level Sensors And Gauging

Knowing the amount of liquid or fluid inside a tank or other vessel is an important variable in any process to maximize process efficiency and help prevent overflows and running dry. This variable is what operators call level. This can be something as simple as a full or empty signal, or it can be a continuous level measurement to track how the level inside changes during a process.

To measure liquid level, there are a number of different technologies used ranging from the simple to very complex. VEGA uses liquid and fluid level sensors, transmitters, and switches with seven different technologies to measure level in a multitude of different applications across at least a dozen key industries.

Liquid Level Sensor Technologies

The technologies at VEGA are: through air radar, guided wave radar, pressure, vibration, capacitance,  radiometric, and ultrasonic. These different measuring methods detect level and convert that level into an electronic signal to be displayed directly at the vessel or incorporated into a process control or management system. Each of these technologies has their pros, cons, and different price points. It comes down to what liquid is being measured, what is happening inside the vessel, and the vessel’s construction.

Radar

How it works

Radar sensors send microwave signals toward the liquid being measured from above. The surface of the liquid below reflects the signals back in the direction of the antenna system. The instrument uses the time of flight for the microwave signals to determine a distance to the product surface, and then calculates a level inside using the known height of the tank or vessel.

Non-Contact Liquid Level Detection

Non-contact liquid level detection sensors using radar technology are trusted to measure liquids with accuracy and reliability. The VEGAPULS series of  radars specializes in continuous liquid level measurement.

VEGA Radar Sensors

VEGA’s radar sensors operate under three different frequencies: C-Band (6.3 GHz), K-Band (26 GHz), and W-Band (75-85 GHz). All three are used for continuous non-contact level measurement for all kind of liquids, even under high pressure and extreme temperatures. They can be used in simple or aggressive liquids, and are suitable for applications with stringent hygiene requirements.

Advantages

  • Non-contact liquid level measurement with high accuracy
  • Measurement not affected by temperature, pressure, foam, or condensation
  • User-friendly adjustment saves time
  • Maintenance-free operation through non-contact measuring principle 
Discover the right radar for your application
 

Guided Wave Radar

How it works

Guided wave radar sensors use time domain reflectometry to measure level.  A cable or rod probe is mounted on top of the tank or vessel, and a low amplitude, high-frequency microwave pulse is sent down the probe to be reflected by the surface of the liquid or fluid. Once the pulse reaches the surface, a portion of the signal bounces back, and the amount of time it takes for the pulse to be transmitted and returned determines the level inside the tank or vessel. Some calibration is required dependent on the liquid’s conductivity.

VEGA Guided Wave Radar

The VEGAFLEX 80 Series can measure a range of liquids even in the presence of steam, buildup, foam, and condensation. Three different probe options – cable, rod, or coax – ensure an accurate measurement for a range of liquids and fluids being measured. A selection of sensors gives operators the ability to make simple measurements as well as measuring aggressive liquids and liquids under extreme pressure or temperature conditions.

Advantages

  • Comprehensive diagnostic options ensure low-maintenance operation
  • Shortenable probes enable simple standardization and maximum flexibility
  • Measurements not affected by steam, pressure and temperature fluctuations, foam, noise, buildup, and condensation
  • Can take measurements in standpipes
Discover the right guided wave radar for your application

Pressure

How it works

Hydrostatic pressure refers to the pressure generated on a cell from the mass of the liquid above it. As level increases inside a tank or vessel, the hydrostatic pressure increases proportionally. Thus, the higher the hydrostatic pressure, the higher the liquid level measurement. To get an accurate level measurement from a pressure transmitter, the density of the fluid must remain fairly constant.

VEGA Pressure Transmitters

The VEGABAR 80 series use different types of diaphragms for different applications. Traditionally, most pressure sensors use an oil filled metallic diaphragm that separates the measuring cell from the process fluid. The VEGABAR 80 series differentiates itself from the competition by including ceramic measuring cells, too. These measuring cells are abrasion-resistant and provides a diaphragm 10 times harder than stainless steel.

Advantages

  • Various configuration options for simple adaptation
  • Multiple mounting configurations including “top down”
  • Reliable measurement with temperatures up to 400˚C
  • Low maintenance with wear-free ceramic measuring cell
  • Accurate measurement to the last drop through the smallest measuring ranges
Discover the right pressure transmitter for your application

Vibration and Capacitance: Liquid Level Switching

How it works

Liquid level switches detect when a certain predefined level is reached by the liquid inside a tank or vessel. These sensors are used when it’s not necessary to measure every possible level, like with continuous level measurement. A switch output can start and stop pumps, sound an alarm, or simply turn on a light. Point level switches can be integrated into a process control system.

VEGA Switches

VEGA uses four different technologies for liquid level switching: vibration, capacitance, microwave barrier, and radiometric.

Vibration switches, part of the VEGASWING series, are contact instruments that monitor frequency. These switches constantly vibrate at a specific frequency. The frequency changes once the liquid or fluid reaches the vibration switch, and this change activates the output.

Capacitance switches, the VEGACAP series, are also contact instruments, but these measure capacitance, or the liquid or fluid’s ability to hold an electrical charge. Once the liquid reaches the switch, the capacitance changes, and the switch output changes state.

Microwave barrier switches use two parts: a transmitter and a receiver. In between is an “invisible” barrier, and the switch is activated once that microwave barrier is broken or interrupted. These switches, called the VEGAMIP at VEGA, can provide “full” or “empty” options, and they can be used to determine when a liquid or fluid is pouring into a vessel. These can also be used as non-contact instruments by shooting through non-conductive vessels.

Lastly, radiometric switches operate similarly in principle to microwave barrier switches, but these instruments use gamma radiation emitted from a source holder while a detector measures the amount of radiation reaching it. Unlike any of the previously mentioned switches, radiometric switches can be installed completely externally, which is why they’re typically used to measure harsh or volatile processes like those seen in oil refining, the chemical industry, and mining.

Advantages

  • Point level detection with low maintenance costs
  • Vibration switches are simple plug and play instruments
  • Capacitance switches work well with continual buildup
  • Microwave barrier switches offer simple adjustment
  • Radiometric switching is completely non-contact
Discover the right liquid level switch for your application

Radiometric

How it works

Radiometric level measurement sounds complicated, but the principle behind it is relatively easy to understand. Gamma radiation emits from a source holder, and a detector measures the radiation that reaches it. The amount of energy reaching the detector will vary based on the amount of liquid inside the tank or vessel. The electronics inside the detector use the gamma reading to infer a measurement and outputs the value.

VEGA Radiometric Sensors

The ProTrac Series is used for continuous level and point level monitoring in the most difficult liquid applications because they measure without contacting the process material. This means there is no chance of damaging the detectors with harsh, abrasive, or corrosive products that would require frequent and expensive maintenance. Plus, these instruments are impervious to thermal shock, drastic pressure shifts, and other extreme process conditions.

Advantages

  • Maximum operational reliability even in the harshest environments
  • Measurement is independent of pressure, temperature, and product aggressiveness
  • Measuring system can be installed on the outside of a vessel during ongoing production
  • Extending existing source life by retrofitting to ProTrac is made easy due to available adapter brackets

Discover the right radiometric instrument for your application

Ultrasonic

How it works

Ultrasonic sensors emit ultrasonic pulses toward the liquid being measured from above. The surface of the liquid below reflects the signals back in the direction of the antenna system. The elapsed time from emission to reception of the signals is proportional to the level of the tank. The instrument uses this time of flight to determine a distance to the product surface, and then calculates a level inside using the known height of the tank or vessel.

VEGA Ultrasonic Sensors

VEGA’s ultrasonic sensors are ideal for simple, standard continuous level applications. The VEGASON sensors are a cost-effective, non-contact solution requiring little to no maintenance. These sensors are compact, allowing for easy installation, and they measure any liquid, independent of the its characteristics.

Advantages

  • Non-contact liquid level measurement with high accuracy
  • Cost-effective solution for simple applications
  • Reliable measurement independent of liquid features
  • Maintenance-free operation through non-contact measuring principle

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