How-to: Choose a Level Sensor
Choose your level sensor, also known as a level switch or level control unit, based on the medium it will be installed in, the level of accuracy the application requires and your budget.
Float switch
- Non-viscous liquids and suspended solids
- Low cost
- Various models for use in different applications (e.g. ATEX or WRAS approved)
- Functional on/off control (e.g. sewage pumps in a pumping station wet well)
- Alarm functions (high/low level alarms)
Conductivity probe
- Non-viscous, clear or greywater
- Low cost
- Functional control on/off control
- Alarm functions
- Suited to precise level switching for non-turbulent mediums
Ultrasonic
- Viscous and corrosive liquids and solids
- Highly accurate and can have logic functions built-in (e.g. setting alarms and pump control)
- Constant level measurements
- Can be used with remote monitoring to view level measurements remotely
- Higher cost to install
Radar
- Viscous, corrosive and turbulent liquids, solids
- Highly accurate and can have logic functions built-in
- Constant level measurements
- Critical level monitoring (e.g. chemical dosing)
- Can be installed externally and read levels through certain tanks (e.g. plastic and polymers)
- Suitable for turbulent environments
Tuning forks
- Solids (specifically powders)
- Low/medium cost and high accuracy
- Available as both digital (on/off/level alarms) and constant level measurements
- Can be mounted directly into pipes
How to choose a level control unit
Choosing the right unit will ensure effective level control and efficient operation. The best level sensor for an application depends on the medium it will be measuring, how accurate the level readings need to be and your budget.
1. Medium
The medium the level control unit is installed in will affect it’s performance and longevity.
Liquids
Contact level sensors, like float switches and conductivity probes, are inexpensive and effective in most liquids.
Float switches are available in a range of designs intended for installation into different liquids, including WRAS and REG4 approved for potable water or ATEX approved for Zone 0 applications. Float switches are not suitable for viscous fluids as it slows their movement and impedes real-time level monitoring.
Conductivity probes are most effective in clear and greywater.
Ultrasonic and radar non-contact level sensors are best for corrosive and viscous fluids, such as chemicals and food processing. Radar is more effective in turbulent environments like tidal applications because their electromagnetic waves are not as easily scattered by adverse weather or dust compared to ultrasonic sound waves.
Solids
Float switches are suitable for use in liquids with a percentage of suspended solids, like wastewater treatment plants, but not in full solids due to the slowed movement.
Conductivity probes are not suitable in applications with any solids content as they can adhere to the conductive rods and interfere with their readings.
Ultrasonic and radar are effective level sensors for bulk solids.
Tuning forks are most effective for fine solids such as powders.
2. Accuracy and Reliability
Different level sensors will work better for on/off applications or for tracking the exact volume of a medium.
Float switches and conductivity probes provide the accuracy required for simple on and off (or filling and emptying) actions such as controlling a pump, solenoid valve or tank levels – with multiple units installed you can set additional high and low-level alarms. The use of multiple units also allows you to track the liquid level between those points, products such as our Ready Level provide a reliable method of fixing multiple floats.
Non-contact level sensors provide constant level readings that are more accurate than contact level sensors, however radar provides greater accuracy than ultrasonic for the most precise level readings in critical applications.
3. Cost
- Float switches and conductivity probes are the most economical due to the extent of their capability.
- Ultrasonic costs more as it provides continuous level readings, and radar is the most expensive due to providing the most accurate level measurements.
- Tuning forks come in at a similar cost to ultrasonic level detection depending on the control requirements of the unit (e.g. on/off control or continuous level detection).
Ask the Experts
For friendly and expert help in choosing the best float switch model for your application, contact our T-T Controls® by calling 01630 647200, emailing ttcontrols@ttpumps.com or completing our online enquiry form.
