Ultrasonic vs radar level meter blind zone calculation guide | 2024 pit selection guide

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Ultrasonic vs radar level meter blind zone calculation guide | 2024 pit selection guide | Doweston

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2025-02-12 Back List

Practical calculation of blind area for liquid level meter installation: 5 key parameters determine success or failure

▶ Calculation of blind zone of ultrasonic liquid level meter

Blind spot distance (B) = λ x τ x C ÷ 4

Calculation example (FTU-20 series ultrasonic level meter)

Working frequency:30kHz → λ = 340m/s ÷ 30,000Hz = 11.3mm
Pulse width:τ = 1ms ( typical value )
Medium sound speed:Water medium C=1480m/s
Calculation result:B = 418mm

※ Actual installation requires an additional 20% safety margin → 418x1.2≈500mm

parameters	Ultrasonic impact	Radar impact
Medium dielectric constant	★★★Change the speed of sound directly	★Only signal attenuation
Temperature fluctuations	1.2% error per 10°C	≤0.03%/ C (with compensation)
Container structure	Flange height is included in the blind zone	Only the beam angle is considered

▶ Radar level gauge blind zone breakthrough technology (FTR-1600 series radar level gauge)

Zero blind zone core technology

▪ 80GHz high frequency modulation → minimum detection 50mm
▪ FMCW frequency modulated continuous wave technology
▪ Dynamic signal filtering algorithm

Comparison of installation solutions

Incorrect installation (ultrasonic)

Distance from tank wall < 0.3D
Echo interference +40%

Correct installation (radar)

Wall-mounted installation + beam angle <3°
Measurement dead zone < 10mm

Key points of engineering practice

▪ Media with dielectric constant ε < 2 require a still-pipe guide
▪ Ultrasonic tilt angle > 30° → blanking zone x 2-3
▪ Installation height for steam conditions ≥5xpipe diameter

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