Doppler radar level gauge is an instrument that measures liquid level by using the Doppler effect. It calculates the liquid level by measuring the frequency change of the radar signal after interaction with the liquid or material.

1. The measurement object is the movement speed: This is the most fundamental difference between it and FMCW radar (distance measurement) and pulse radar (distance measurement). Essentially, it is a non-contact speed sensor.
2. Sensitive to movement, insensitive to stillness: Only when the liquid surface or particles are in motion does it have an effective signal output. A completely still liquid surface will produce an echo with the same frequency as the transmitted frequency, without frequency shift, and thus cannot be effectively detected.
3. Non-contact and wear-free: Compared with mechanical flowmeters or contact liquid level gauges, it is suitable for abrasive and corrosive media.
4. Simple installation: Usually, it only requires a hole to be drilled on the top of the tank for installation.

1. Open channel / non-full pipe flow measurement: This is the main application. Install it above the channel or pipe to measure the flow velocity of the water surface. Combined with the known cross-sectional shape and water level height (usually requiring a separate level gauge), the volume flow can be calculated.
2. Solid level switch / flow monitoring:
   • Level switch: Install it on the side or top of the silo. When solid particles (such as plastic pellets, grains, coal powder) are falling or flowing, the sensor can detect the movement and output a switch signal for high-level or low-level alarm to prevent overflow or idling.
   • Chute / drop pipe flow monitoring: Monitor whether solid materials are flowing, blocked or cut off in the conveying pipe or chute.
3. Special liquid level measurement:
   • For measuring liquid surfaces with severe fluctuations or agitation. Traditional distance-measuring radars may have unstable signals due to waves, while Doppler radar takes advantage of such fluctuations to generate signals.
   • For measuring liquid surfaces covered with foam. The foam layer itself may be in motion and can be detected.

Doppler radar level gauge is a specific-purpose instrument that generates signals through motion. It is not a traditional "level gauge" used to measure static height, but rather more like a "motion detector" or "flowmeter". The right time to choose it is when you need to monitor whether materials are flowing, measure the flow in open channels, or detect fluctuating material level switches.