Accurate acquisition of ocean hydrological parameters is the core basis for revealing ocean circulation patterns, studying ecosystem changes, and carrying out resource exploration and climate assessment. The CTD series temperature and salt depth detector (CTD, the abbreviation of Conductivity, Temperature, and Depth) is the core equipment in the field of ocean survey. With the advantages of multi-parameter synchronous monitoring, high-precision data output, and full-sea adaptation, it replaces traditional distributed measurement tools and has become the standard equipment for scientific research vessels such as "Xuelong 2" and "Ocean 6" and various underwater platforms, providing reliable data support for marine scientific research and marine engineering practice.
1. Core technical principles: multi-sensor collaborative hydrological detection logic

The CTD series temperature and salt depth detector adopts the core working principle of "multi-sensor integration + digital analysis" to achieve simultaneous and accurate capture of key seawater parameters. The core of the equipment is equipped with high-precision temperature sensors, conductivity sensors and pressure sensors, and the integrated design ensures measurement synchronization. Temperature measurement relies on platinum resistors or semiconductor sensing elements, utilizing the characteristics of material resistivity that changes with temperature to achieve accurate sensing. The response time is as fast as 150 milliseconds, and can capture the subtle temperature gradient of the water body. The conductivity sensor detects the conductivity of seawater to infer the salinity value, and combines the temperature compensation algorithm to eliminate the interference of water temperature on the measurement results to achieve accurate conversion of salinity. The depth measurement uses a pressure sensor to capture changes in seawater static pressure, and combines seawater density parameters to derive the actual water depth, which can cover up to 6,000 meters of deep sea exploration needs.

The entire system is equipped with a data acquisition module and a real-time transmission unit. During the process of lowering the detector, it can complete full parameter sampling once or more per second. The data is received, analyzed and stored in real time by the deck control system. At the same time, the equipment can be mounted with a water sampling device (usually composed of 24 or 36 water sampling tanks), and automatically shuts down to collect water samples at a preset water depth, realizing the dual function of "in-situ monitoring + sample collection" and providing physical samples for subsequent laboratory analysis. Some high-end models also support the expansion of sensors such as turbidity, dissolved oxygen, chlorophyll, and methane to build a multi-dimensional marine environment monitoring system.

2. Product core features: comprehensive upgrade of accuracy and adaptability

After multiple generations of technology iterations, the CTD series temperature and salt depth detectors have developed significant advantages in measurement accuracy, environmental adaptability, and functional scalability, and can meet the diverse detection needs from shallow seas to deep seas, and from offshore to polar regions.

1. High-precision synchronization and reliable data

The temperature measurement range covers -2°C to 36°C, with an accuracy of ±0.005°C, and a resolution as low as 0.0006°C, which can accurately capture subtle changes in the ocean thermocline; the conductivity measurement range is 0-70mS/cm, with an accuracy of ±0.003mS/cm, combined with the salinity conversion model, can achieve high-precision output of salinity; depth measurement relies on pressure sensing technology to maintain excellent stability in the range of 0-6000 meters, providing guarantee for deep-sea profile detection. The multi-parameter synchronous sampling design avoids the time difference error of scattered measurements and ensures the relevance and accuracy of data.

2. Seawide adaptability, excellent protection

It adopts high-strength anti-corrosion shell, optional 316 stainless steel or special marine-grade composite materials, which can effectively resist seawater corrosion, high-pressure extrusion and biological adhesion, and its protective performance meets the requirements of deep-sea exploration. The equipment can adapt to water temperature environments ranging from -2°C to 35°C. Some polar-specific models are equipped with anti-icing modules and can operate stably in severe cold sea areas such as Antarctica and the Arctic. Whether it is the 4,500-meter deep sea in the southeastern Pacific or the polynya on the front edge of the Ross Ice Shelf, reliable detection operations can be completed.

3. Flexible expansion and diverse scenarios

The series of products covers ship-borne, submersible, abandonment, underwater platform-mounted and other types, adapting to different detection scenarios. The ship-mounted type is lowered by a winch and can complete vertical profile detection at fixed-point stations; the disposable type is a single-use device that transmits data in real time through optical fiber, and is suitable for rapid census of large areas of sea; the submersible type is adapted to underwater platforms such as AUV and ROV, and can achieve long-term fixed-point monitoring or mobile detection. At the same time, it supports multi-sensor expansion, and can add water quality and biological parameter monitoring functions according to needs, and build an integrated marine environment detection system.

4. Intelligent, convenient and efficient in operation

Equipped with a deck control system and a Chinese operation interface, parameters such as sampling depth and water extraction trigger conditions can be preset. During the lowering process, data such as depth, temperature, and salinity are displayed in real time as well as change curves, making it easier for scientific researchers to judge the water structure in real time. The water collector can achieve precise sampling through remote control, and the recovered data can be directly exported to the analysis software, supporting seamless connection with the marine survey database, greatly improving operational efficiency. The entire set of equipment, from deployment, detection to recovery, can be operated by a single person with a winch, adapting to the complex offshore operating environment.

3. Key technical parameters: accurately matching ocean detection needs

The CTD series temperature and salt depth detector parameter configuration covers multiple scenarios. The core technical parameters are as follows (taking mainstream shipborne models as an example):

- Measuring range: temperature -2℃~+36℃, conductivity 0~70mS/cm, depth 0~6000m (expandable), salinity derivation range 0~42psu;

- Accuracy and resolution: temperature accuracy ±0.005℃, resolution 0.0006℃; conductivity accuracy ±0.003mS/cm, resolution 0.001mS/cm; depth accuracy ±0.1%FS;

- Sampling performance: maximum sampling frequency 1Hz and above, response time ≤150ms, supports multi-depth fixed-point water extraction control;

- Protection and adaptation: Anti-corrosion shell, suitable for seawater pressure environment, supports DC wide voltage power supply, and data transmission supports wired optical fiber or wireless communication;

- Expanded functions: Can mount 24/36 tank water collectors, supports expansion of dissolved oxygen, turbidity, chlorophyll and other sensors, and is suitable for various platforms such as ship-borne and submersible buoys.

4. Multi-field applications: from scientific research to engineering value realization

As a "basic tool" for marine surveys, the CTD series temperature and salt depth sounders have been applied in depth in many fields such as scientific research and exploration, resource development, and climate monitoring, and have become the core support for the development of marine undertakings.

1. Polar and Oceanic Scientific Expeditions

In Arctic and Antarctic scientific expeditions, CTD detectors are the core means of water environment investigation. During the expedition in the Arctic Ocean, the "Xuelong 2" detected extremely high chlorophyll peaks through CTD detection, up to 200 milligrams per cubic meter, which provided key data for studying the formation mechanism of "marine snow" and the Arctic biological carbon pump; during the expedition into the Amundsen Sea and Ross Sea in Antarctica, CTD was used to obtain temperature and salinity characteristic data at different water depths, providing support for analyzing the impact of glacier melting on the marine ecosystem.

2. Marine resource exploration

In oil and gas resources and deep-sea mineral exploration, CTD detectors are used to analyze the hydrodynamic environment of the sea area and provide data reference for drilling platform site selection and pipeline laying. By monitoring seawater temperature and salinity distribution, the direction of ocean currents can be inferred and the impact of the environment on engineering facilities can be assessed; in hydrothermal area detection, combined with the expanded functions of turbidity and methane sensors, the hydrothermal activity area can be quickly located and provide clues for mineral resource exploration.

3. Climate and ecological monitoring

In global climate change research, CTD long-term monitoring data can be used to analyze changes in ocean temperature and salt structure and reveal the regulatory effect of ocean circulation on climate. In coastal waters, CTD can be used to monitor water body temperature and salinity gradients and dissolved oxygen content to assess the risk of ecological disasters such as red tides and green tides, providing scientific basis for marine ecological protection and fishery resource management.

4. Marine Engineering and National Defense Security

In port construction and cross-sea projects, CTD detectors are used to monitor hydrological parameters in offshore waters to provide guarantee for engineering design and construction safety. In the field of national defense, disposable CTDs can be used to quickly obtain temperature and salt profile data in large areas of the sea, providing environmental parameter support for submarine navigation and anti-submarine operations, and improving the ability to perceive the underwater combat environment.

5. Industry value and development prospects

At present, domestic CTD series temperature and salt depth detectors have gradually narrowed the gap with international products in terms of high precision, miniaturization, reliability, etc. Some models have achieved breakthroughs in key technologies such as anti-pollution and dynamic correction, filling the gap in the field of domestic deep-sea environmental monitoring. As the core equipment of the marine precision monitoring system, its widespread application not only promotes the in-depth development of marine scientific research, but also helps my country master the core data voice in polar scientific expeditions, deep-sea exploration and other fields, which is in line with the policy orientation of building a maritime power and high-quality meteorological development.

In the future, with the integration of artificial intelligence and Internet of Things technology, the CTD series detectors will be further upgraded: integrating machine learning algorithms to optimize data analysis accuracy to achieve prediction and early warning of marine phenomena; developing miniaturized, low-power models to adapt to more underwater mobile platforms; building a multi-device network monitoring system to achieve three-dimensional and normalized monitoring of sea areas. At the same time, driven by the "double carbon" goal, it will play a greater role in emerging fields such as marine carbon sink measurement and climate regulation assessment, and continue to inject scientific and technological power into unlocking the mysteries of the ocean, protecting marine ecology, and developing marine resources.