An ultrasonic level sensor measures how far the liquid surface is from the sensor face by timing a sound pulse, which makes it the usual first choice for clean water, chemical day tanks and sumps where nothing should touch the liquid. It is not the only choice: radar suits vapour, condensate and narrow tanks, and a submersible sensor suits foam and turbulence. This guide compares the three continuous 4-20 mA technologies and shows which Icon Process Controls level sensor ERE carries for each tank.
In this guide
- What are the main types of continuous level sensor?
- When does an ultrasonic level sensor work best?
- When is a radar level transmitter worth the cost?
- Why choose a submersible level sensor?
- What about float and tuning fork switches?
- How do the technologies compare side by side?
- How do you choose a level sensor, step by step?
- Do Canadian tank rules affect the choice?
- Which level sensors does ERE carry?
- Frequently Asked Questions
What Are the Main Types of Continuous Level Sensor?
Three technologies cover most water, wastewater and chemical tanks: ultrasonic (sound pulse from above), radar (microwave pulse from above) and submersible hydrostatic (pressure sensor on the tank bottom). A fourth, the magnetic-float stem sensor, gives a continuous 4-20 mA signal over a short range. All four feed a PLC, a display or a level controller.
Point (switch) devices are a separate family: they answer "is the liquid at this height?" rather than "how high is it?". We cover those in our float switch guide, and the loop wiring and scaling in our 4-20 mA transmitter guide.
When Does an Ultrasonic Level Sensor Work Best?
An ultrasonic level sensor works best on clean liquids in open or vented tanks with a clear path between the sensor and the surface. The sensor sends a sound pulse down, times the echo and converts the distance into level, so nothing contacts the liquid and chemically aggressive contents are not a wetted-material problem.
ERE carries three Icon ultrasonic options:
- Icon UltraPro 500: loop-powered, narrow-beam, PVDF transducer, 2-wire 4-20 mA with HART or RS-485 Modbus, NEMA 4X / IP67 enclosure and push-button programming.
- Icon UltraPro 2000: 2-wire ultrasonic transmitter with a PTFE transducer, 5 m or 10 m range, general-purpose or explosion-proof versions.
- Icon ViewSonic VSL-200-RD: battery-operated, wireless to a remote display, 0 to 15 m, for tanks where running cable to the display is the expensive part.
Where it struggles: foam absorbs the pulse, heavy vapour or condensate on the transducer weakens it, and every ultrasonic unit has a blanking distance below its face where it cannot read. Mount it so the highest liquid level stays outside that zone, and away from the fill line. If the tank has foam or fuming, go to radar or submersible.
When Is a Radar Level Transmitter Worth the Cost?
A radar level transmitter is worth the extra cost when the tank has vapour, condensate, turbulence or a narrow neck, because the microwave pulse is not weakened by those conditions the way a sound pulse is. Icon describes its radar line for exactly that duty.
| Model | Technology | Notes from the product record |
|---|---|---|
| ProScan 3 | 80 GHz radar | 3° beam angle, 2 in dead band, 2 in NPT, polypropylene transducer, Bluetooth set-up, 4-20 mA with RS485, rapid telemetry and LoRa versions |
| ProScan 2 | 80 GHz radar | 2 in dead band, loop-powered 4-20 mA (HART optional), PTFE or 316 SS antenna, NPT or flange |
| ProScan 26GHz | 26 GHz radar | Loop-powered, PTFE or 316 SS antenna, plastic enclosure, NPT or flange |
| MLR-70 | Guided-wave radar | FEP-coated stainless rod or rope electrode, G1 in thread, 4-20 mA with HART, explosion-proof and high-temperature versions |
The practical difference between the two radar styles: non-contact radar (ProScan) shoots through the air space like an ultrasonic unit but with a narrow beam, while guided-wave radar (MLR-70) sends the pulse down a probe that touches the liquid, which suits narrow vessels, stilling wells and surfaces that move. The product records give no accuracy figure for the radar models, so ask us for the manufacturer data sheet if your control loop needs a specific tolerance.
Why Choose a Submersible Level Sensor?
A submersible level sensor is the right choice when foam, vapour, condensate or turbulence would defeat a sensor mounted above the liquid. It sits on the tank bottom and measures the pressure of the liquid column above it. Water produces roughly 1 psi for every 2.31 ft of depth, so the pressure reading converts directly to level; denser or lighter liquids need the specific gravity entered at set-up.
Icon's submersible range, all with an integral molded weight so the sensor does not float, a PTFE-jacketed cable and Kalrez O-rings:
- 100 Series: ceramic diaphragm, ±0.5%, housings in PVC, PP, PVDF, PTFE or 316 SS, standard 0 to 34 ft range.
- 200C Series: capacitive ceramic diaphragm, ±0.25% accuracy, same housing choices.
- 300S Series: 316 stainless body and diaphragm, ±0.5% of full scale, 4-20 mA, ratiometric, voltage or RS485 output.
- TankPro: sensor plus a loop-powered LED display in one unit, so the level reading is at the tank; ceramic diaphragm, ±0.5%, 2 in NPT.
Trade-offs: the sensor is wetted, so the housing material must suit the liquid, and solids that settle on the diaphragm need an occasional clean. Tank-top fittings such as the LP75 thru-point connector and the LP100 junction box (Gore-Tex breather for the atmospheric reference) complete the install.
What About Float and Tuning Fork Switches?
Use a switch when you only need alarm or pump-control points, not a continuous reading. The Icon CFL is the in-between option: a magnetic float on a stem with a 4-20 mA output, ±2 mm accuracy and a measuring length to 6 ft, in PVC, PP, PVDF or 316 SS. For vibrating-fork point detection that tolerates foam, turbulence and viscous liquids, look at the Icon TFS; for sensing through a plastic or fibreglass wall without drilling the tank, the Icon NC30 reads through walls up to 8 mm thick.
How Do the Technologies Compare Side by Side?
| Tank condition | Ultrasonic | Radar | Submersible |
|---|---|---|---|
| Clean liquid, open or vented tank | Good fit | Works, higher cost | Works |
| Foam on the surface | Poor | Check with supplier | Not affected |
| Vapour or condensate | Weakened | Designed for it | Not affected |
| Aggressive chemical | Non-contact; transducer faces vapour | Non-contact or PTFE-wetted probe | Wetted; choose housing material |
| Narrow tank or obstructions | Beam can hit the wall | 3° beam or guided wave | Not an issue |
| Sludge or settling solids | Fine | Fine | Diaphragm may need cleaning |
| Wiring to the display | 2-wire loop or wireless (ViewSonic) | 2-wire loop | Cable down the tank |
How Do You Choose a Level Sensor, Step by Step?
- Write down the liquid and its temperature range, and whether it foams, fumes or crystallizes.
- Measure the tank: height from the mounting point to the empty level, and the diameter of the neck or opening.
- Check for obstructions: ladders, pipes, agitators and fill lines in the sensor's path.
- Pick the technology from the table above: ultrasonic for clean, radar for vapour or a narrow neck, submersible for foam.
- Match the range: the UltraPro 2000 comes in 5 m and 10 m, the ViewSonic reads to 15 m, submersible units start at 0 to 34 ft.
- Confirm the output your PLC or controller takes: 4-20 mA, HART, RS-485 Modbus, or wireless.
- Check the area classification: the UltraPro 2000 and MLR-70 have explosion-proof versions.
- Plan the display and alarms: pair the sensor with a level controller such as the Icon ITC 450, which accepts 4-20 mA and has relay outputs and Modbus.
Do Canadian Tank Rules Affect the Choice?
They can, for petroleum and allied petroleum storage. The federal Storage Tank System for Petroleum Products and Allied Petroleum Products Regulations (SOR/2008-197) define a storage tank system to include overfill protection devices, and its Schedule 4 points to CAN/ULC-S661, the standard for overfill protection devices on flammable and combustible liquid tanks. A process level transmitter does not replace a certified overfill device, so ask your tank installer which device the regulation requires and use the transmitter for inventory and alarms.
For comparison, the US EPA lists automatic tank gauging systems as one accepted internal release-detection method for underground tanks. Provincial and municipal requirements vary, so confirm with the authority having jurisdiction before you specify.
Which Level Sensors Does ERE Carry?
ERE carries the Icon Process Controls level range, ultrasonic, radar, submersible, float and tuning-fork, plus the brackets, bulkhead fittings and junction boxes, in the Level Sensors & Switches collection. For the signal side, see our process pH and conductivity sensor guide, and for flow on the same line, the flow meter guide. ERE has supplied Canadian industrial and environmental customers since 1994, so send us the tank and we will match the sensor.
Need help picking a level sensor?
Tell us the liquid, the tank height and neck size, and the signal your PLC takes. We will match the technology, range and housing material.
→ Request a Quote | 1-888-287-EREC | Browse Level Sensors | sales@ereinc.com
Frequently Asked Questions
How does an ultrasonic level sensor work?
It sends a sound pulse from the top of the tank toward the liquid surface, times the echo and converts the travel time into a distance, which the transmitter scales into level and outputs as 4-20 mA or a digital signal.
Ultrasonic or radar level sensor: which is better?
Ultrasonic is simpler and lower cost for clean liquids in vented tanks. Radar is the better choice with vapour, condensate, turbulence or a narrow neck, because the microwave pulse is not weakened by them.
Which level sensor works with foam?
A submersible sensor, which measures pressure at the tank bottom and is not affected by foam, vapour, condensate or turbulence. A tuning fork switch also works through foam for point detection.
What is a dead band or blanking distance?
The zone just below the sensor face where it cannot measure. Mount the sensor so the maximum liquid level stays out of it; Icon lists a 2 in dead band for its 80 GHz ProScan radar models.
Can a level transmitter replace an overfill prevention device?
Not by itself in regulated petroleum storage. Federal regulations point to CAN/ULC-S661 certified overfill protection devices, so use the transmitter for monitoring and confirm the required device with your installer.
Related articles
- Float Switch Guide: Choose by Float Type, Wetted Material and Contact
- 4-20mA Pressure Transmitter Buyer's Guide for Canada
- Process pH and Conductivity Sensors: How to Choose
- Flow Meter Guide: Ultrasonic, Magnetic, Paddle Wheel or Turbine
Lire en français : Capteurs de niveau ultrasoniques, radar et submersibles : guide de choix pour les réservoirs au Canada