Illustrated Examples of Common Level Technologies
Level/Float Switches
One of the simplest and most cost-effective technologies for measuring level, level/float switches are used in liquid applications, with one or more set point per switch. Often used as High/Low level switches, systems can also be designed for use with High/High and Low/Low alarming set points for control.
Consisting of a mechanical float(s) moving up and down a rod or a radio frequency balanced impedance bridge, switches provide a digital signal output, either at the location or remotely, which can easily be inputted into a control or remote monitoring system.
Benefits:
Very cost effective
Simple to set up
Easy to use
Can be used as standalone devices (some have alarms built into them)
Manufacturers:
Babbit, Barksdale
Applications:
Water/Chemicals/Fuels
High/Low Level Alarm
Auto Tank Filling or emptying
Sump Controls
Pulse Radar
Also called non-contact radar, Pulse Radar technology is commonly used in difficult applications, often featuring multi-media material, where non-contact and high accuracy are important. An electronic pulse is directed at the fluid’s surface and then reflected back at the antenna, the round trip time is then calculated to determine the fluid level in the container. Providing an anolog output (4-20mA) as well as options for digital communications, the signal can be tied directly into a control or remote monitoring system.
Benefits:
Can measure any material with the dielectric constant greater than two
Measures multi-media material
Non-contact
High Accuracy
Most cost-effective on larger tanks
Manufacturers:
Babbit, Honeywell
Applications:
Water/Wastewater
Chemicals/Acids/Caustics
Slurries
Food and Beverage
Guided Wave Radar
The go-to technology for tough applications, especially powder and oil and gas applications, as well as measuring in tight spaces. Guided wave radar sends a radar signal down a cable running the length of the tank and provides an analog (4-20mA) output signal for input into a control or remote monitoring system.
Benefits:
Can read materials with a very low dielectric number
Measures multi-media material
High accuracy
Remote mount electronics
Can measure hundreds of vertical feet
Manufacturers:
Babbit, Honeywell
Applications:
Accumulators
Extreme pressure variations or pressurized containers
Multi-use tanks
Liquefied gas containers
Items with low dielectric qualities
Raw materials and Polymer Powders
Ultrasonic
Ultrasonic level measurement is the most common, cost-effective, non-contact level measurement technology. By sending an ultrasonic wave toward the liquid surface, level can be reliably calculated by measuring the signals transit time. The analog output (4-20mA) signal can be inputted into a control or remote monitoring system. Different ultrasonic form factors are available for use in solid, liquid, and slurry applications.
Benefits:
Cost-effective solution
Reliable accurate
Non-contact
Ease of installation and reduced maintenance
Self-contained, battery powered, wireless units available
Manufacturers:
Babbit, Banner, Honeywell, Turck
Applications:
Water/Wastewater
Chemicals/Oils
Viscous Fluids/Slurries
Food and Beverage
Solids
Level Sight
Commonly used in non-critical applications, Level Sight or Sight Glass is mounted to the exterior of a tank and ensures reliable, real-time visualization of a tank’s level.
Benefits:
Inexpensive
Direct read
Good visual back-up
Measures most liquids
Manufacturers:
Babbit, Barksdale
Applications:
Most liquids
Differential Pressure Transmitter
Using one externally mounted transmitter, differential pressure level technology compares the differential pressure reading from the top or “head” of the tank to the one at the bottom of the tank. Due to the precision of pressure measurement, the calculated level is very accurate and highly precise. An analog (4-20mA) output signal, as well as other communications protocols are offered for use in a control or remote monitoring system.
Benefits:
Very accurate
Tank size and shape are not as important
Cost effective
Can measure most liquids
Manufacturers:
Honeywell, Wika
Applications:
Pressurized or open air tanks
Liquids or Light Slurries with a diaphragm
Water/Wastewater
Chemicals/Oils
Food and Beverage
