Underwater depth gaugeIt is a key device that uses acoustic principles to measure water depth. Its core principle is based on sound wave reflection ranging, which calculates water depth by emitting sound waves and receiving the signals reflected back from the seabed, combined with sound velocity. The following is a detailed analysis of its working principle:

1、 Core principle: Sound wave reflection distance measurement

Acoustic emission:

　　Underwater depth gaugeTransmit high-frequency sound wave pulses (usually 200kHz or 500kHz) to the seabed through a transducer (underwater sound wave transmission/reception device).

Sound waves propagate in the form of spherical waves in water, and their energy gradually decays.

Sound wave propagation and reflection:

Sound waves reflect off underwater or underwater obstacles, forming echo signals.

The reflection intensity depends on the acoustic properties of seabed materials such as rocks and sediments, with hard surfaces reflecting more strongly.

(Divided by 2 because the sound wave travels back and forth once)

2、 Sound speed correction: key accuracy guarantee

The speed of sound is affected by seawater temperature, salinity, and pressure, and requires real-time calibration to ensure measurement accuracy:

Factors affecting sound velocity:

Temperature: The speed of sound increases with temperature (approximately+1.7m/s/℃).

Salinity: For every 1 ‰ increase in salinity, the sound velocity increases by approximately+1.3m/s.

Pressure: For every 100m increase in depth, the speed of sound increases by approximately+1.7m/s.

Correction method:

Built in sensors: Some depth gauges integrate temperature, salinity, and pressure sensors to automatically calculate sound velocity.

External input: Obtain data through preset sound velocity values or by connecting an external sound velocity meter (such as CTD).

Empirical formula: Using empirical models such as the UNESCO sound velocity algorithm, calculate the sound velocity based on temperature salinity depth (TSD) data.

3、 Technical implementation: Differences between single beam and multi beam

1. Single beam depth gauge

Principle: Transmit sound waves in a single direction and measure water depth in the vertical direction.

Features:

Simple structure, low cost, suitable for shallow water or fixed-point measurement.

The measurement result is a single point water depth, which requires mobile devices to obtain data from multiple points.

Representative products: Tritech PA200/PA500.

PA200: 200kHz frequency, measurement range 0.7-100m, resolution 1mm.

PA500: 500kHz frequency, measurement range 0.3-50m, resolution 1mm.

2. Multi beam depth meter

Principle: Simultaneously emitting sound waves from multiple directions to form a fan-shaped or three-dimensional scanning area.

Features:

Wide coverage, high data density, and the ability to simultaneously obtain the water depth of multiple points.

Suitable for large-scale surveying tasks such as terrain mapping and seabed resource exploration.

Representative product: Tritech Gemini series multi beam image sonar.

Generate high-resolution underwater topographic maps through beamforming technology.