— Radar vs Float vs Hydrostatic vs Ultrasonic – Which One Should You Choose?

Storage tanks are the backbone of industrial facilities—from crude oil terminals and chemical depots to food processing plants and water treatment works. Accurate level measurement is not just about inventory management; it directly impacts safety (overfill prevention), product quality, process efficiency, and regulatory compliance-1.

But with so many technologies available—radar, float, hydrostatic, ultrasonic, capacitance, servo—how do you choose the right one? This guide compares the most common level measurement technologies for storage tanks, helping you match the right solution to your application.

1. Radar Level Measurement

Radar (microwave) level transmitters are increasingly the technology of choice for modern storage tanks-. They emit high-frequency electromagnetic waves toward the product surface and measure the time taken for the signal to return.

How it works: A radar transmitter sends microwave pulses from a top-mounted antenna. The signal reflects off the liquid surface and returns to the antenna. The transmitter calculates the distance based on the time-of-flight (pulsed radar) or frequency difference (FMCW radar)-.

Two main types:

Key advantages:

• Non-contact: Top-mounted, does not touch the product surface, minimising contamination risk-

• Unaffected by density, viscosity, or temperature changes--1

• High accuracy: ±1 mm or better achievable-; FMCW radar can achieve accuracy to within 0.5 mm--31

• Immune to vapours: Performance unaffected by heavy vapours or gas density-

• Minimal maintenance: No moving parts means virtually no wear-1

• No calibration required-1

Limitations:

• Higher initial cost compared to float or hydrostatic technologies-7

• Performance can be affected by very low dielectric materials (ε < 1.5–2)-7

• Non-contacting radar may have signal attenuation in some applications with low dielectric media-20

Best applications: Crude oil storage, refined products, chemicals, LNG/LPG, water treatment, and any application requiring high accuracy with minimal maintenance-16.

2. Float Level Measurement

Float-based devices are among the simplest and oldest level measurement technologies-7. A float moves with the liquid surface, and its position is translated into a level reading via mechanical or magnetic means-.

How it works: A buoyant float rises and falls with the liquid level. The float's movement is transmitted through a chain, cable, or magnetic coupling to an indicator or transmitter-.

Key advantages:

• Simple and reliable: Well-understood technology with no complex electronics

• Unlimited tank height: Can be used in very tall tanks--7

• Good accuracy: Depending on the float type and sensing mechanism--7

• Low cost: Comparatively inexpensive--7

• Insensitive to density changes-

• Works in foamy media: Unlike ultrasonic, floats can provide accurate readings in foam-

Limitations:

• Intrusive: The float contacts the product, creating contamination risk--7

• Mechanical wear: Moving parts subject to wear, corrosion, and mechanical failure-7

• Can get stuck: Material buildup can prevent free movement--7

• Weight changes: Material buildup can affect float weight and accuracy-7

• Limited to clean liquids: Not suitable for viscous, dirty, or crystallising media-

• Not suitable for pressurised tanks: Generally used in open or atmospheric tanks-

Best applications: Open tanks, water storage, non-corrosive liquids, backup/visual indication, and applications where cost is the primary driver-24.

3. Hydrostatic (Pressure-Based) Level Measurement

Hydrostatic level measurement uses the principle that pressure at the bottom of a liquid column is directly proportional to the height (level) of the liquid-24.

How it works: A pressure or differential pressure transmitter measures the hydrostatic pressure at the bottom of the tank (or the differential pressure between bottom and top for closed tanks). Level is calculated using the formula: $P=\rho \times g\times h$, where $P$ is pressure, $\rho$ is density, $g$ is gravity, and $h$ is height-24.

Key advantages:

• Cost-effective: Generally lower cost than radar or guided wave radar-

• Works with irregular tank shapes: Tank geometry does not affect hydrostatic pressure-

• Tolerant of foam and turbulence: Unaffected by surface conditions that can disrupt other technologies-

• Any tank size: Can accommodate any size tank-

• Wide media compatibility: Works with almost any liquid media-

Limitations:

• Density dependent: Requires knowledge of liquid density; density changes cause measurement errors-24

• Cannot measure interfaces: Cannot distinguish between two liquids in the same tank-

• Limited accuracy: Generally moderate accuracy compared to radar-

• Zero-point drift: Pressure transmitters may experience drift over long-term operation-

• Contact measurement: The sensor contacts the media (unless using a remote seal)

Best applications: Open tanks, general-purpose liquid tanks, water/wastewater, fuel storage, and applications where density is stable and high accuracy is not required-24.

4. Ultrasonic Level Measurement

Ultrasonic level transmitters emit sound waves and calculate level based on the time taken for the echo to return-7.

Key advantages:

• Non-contact: No product contamination

• Cost-effective: Lower cost than radar

• Simple installation: Easy to install and configure-16

Limitations:

• Affected by foam: Foam absorbs sound waves, causing errors-16

• Affected by heavy vapours: Vapours can attenuate the signal-7

• Temperature sensitive: Accuracy affected by temperature changes-7

• Dust and ambient noise: Can interfere with readings-7

• Limited performance in challenging conditions: Radar is preferred for difficult applications-16

Best applications: Water tanks, open-top tanks, hygienic applications with predictable conditions, and cost-sensitive applications where conditions are stable-24-.

5. Comparison Summary Table

6. How to Choose the Right Technology

Use this decision framework to guide your selection:

Step 1: Is high accuracy (≤±1 mm) required?

• Yes → Radar (non-contact or guided wave)

• No → Consider hydrostatic, ultrasonic, or float

Step 2: Is the media corrosive, volatile, or hazardous?

• Yes → Radar (non-contact) – isolates the instrument from the media

• No → Consider other options

Step 3: Is there foam, agitation, or turbulence?

• Yes → Guided wave radar or hydrostatic (both tolerate surface conditions)--16

• No → Non-contact radar or ultrasonic may work

Step 4: What is the dielectric constant of the media?

• Low (ε < 2) → Guided wave radar is preferred-20

• High (ε > 2) → Non-contact radar works well-20

Step 5: Is density stable?

• Yes → Hydrostatic is viable

• No → Radar (density changes do not affect accuracy)

Step 6: What is your budget?

• Low → Float or hydrostatic

• Medium → Ultrasonic (if conditions permit)

• High / Critical application → Radar

7. Common Mistakes to Avoid

8. Why Choose Anhui Tiankang for Storage Tank Level Measurement?

Anhui Tiankang (Group) Co., Ltd. has been manufacturing industrial instruments for nearly five decades. Our level measurement portfolio covers the full range of technologies discussed in this guide:

Radar Level Transmitters (TKLD Series) :

• 80 GHz high-frequency non-contact radar – narrow beam, high accuracy even with vapours and agitators-16

• Guided wave radar – for low dielectric, foaming, and turbulent applications-16

• Ex d/Ex ia certified for hazardous areas

• Accuracy up to ±1 mm

Hydrostatic Level Transmitters (TK1151/3051 Series) :

• Gauge pressure, absolute pressure, and differential pressure configurations

• Remote diaphragm seals for viscous or corrosive media

• Cost-effective solution for general-purpose tanks

Level Switches :

• Vibrating fork switches for overfill protection

• Capacitance switches for solids and liquids

Complete certifications – CCC Ex, ATEX, IECEx, SIL, CCS marine

Proven track record – Long-term supplier to CNPC, Sinopec, CNOOC, and international EPC projects

9. Conclusion

There is no single "best" level measurement technology – the right choice depends on your specific application:

With nearly five decades of experience and a complete range of level measurement technologies, Anhui Tiankang can help you select the right solution for your storage tanks.

Contact Us

For level measurement selection advice, technical documentation, or project quotations, please contact:

Yin Shuangjie
International Sales Manager
📧 Email: [email protected]
📱 WhatsApp / Zalo: +86 17856068126
🌐 Website: http://www.tiankang-global.com/

Anhui Tiankang – Your partner for reliable storage tank level measurement solutions.