Long-term underwater temperature monitoring is unforgiving. Sensors are immersed for years at a time, exposed to changing water chemistry, biofouling, pressure cycles and electrical noise from nearby equipment. If your temperature transmitter is not robust and stable, you will spend your budget on call‑outs, recalibrations and replacements instead of collecting usable data.
The STT-28 SDI-12 Submersible Temperature Transmitter from Stork Solutions is designed specifically to avoid that scenario. It combines rugged mechanical design with digital SDI-12 communications and carefully selected sensing electronics to deliver accurate, low-drift data in a form that is easy to integrate and maintain.
Why Underwater Temperature Monitoring Is So Demanding
Before looking at the STT-28 itself, it is worth spelling out what makes submersible temperature measurement difficult, based on typical use-cases seen across environmental and industrial monitoring:
- Continuous immersion and ingress risk
Housing, seals and cable entry must remain watertight for years. Any moisture ingress quickly affects readings or causes failure. This is especially critical in seawater or chlorinated water where corrosion is aggressive. - Media compatibility and corrosion
Freshwater, seawater, industrial process water, wastewater and chemically treated water all have different corrosion profiles. Poor material choices lead to pitting, stress corrosion cracking and ultimately sensor failure. - Stability and drift over years
Long-term monitoring projects (groundwater trend analysis, harbour monitoring, climate studies) often run for many years. Sensors must demonstrate low drift and repeatability over time to avoid frequent recalibration or data reprocessing. - Variable thermal dynamics
Some applications prioritise trend accuracy over minutes or hours (e.g. tanks, reservoirs, estuaries). Others need fast response to rapid changes (e.g. tsunami-related disturbances, thermal fronts, process upsets). A one‑size‑fits‑all sensor rarely serves both perfectly. - Power budgets and remote deployments
Many SDI-12 based monitoring systems are battery or solar powered. Sensors must operate with low power consumption, and support multi-drop networks without overloading the logger or power system. The SDI-12 standard is widely used in such applications because of its low power serial data interface and multi-sensor support. - Integration and data quality
Environmental monitoring systems often mix level, pressure and temperature sensors. Stork’s own SLS-D Digital Submersible Level Transmitter – SDI‑12 is a good example in the level domain, providing both level and temperature via SDI‑12 for environmental monitoring and flood defence source: SLS-D product page. A temperature-only device like the STT‑28 needs to communicate with the same level of robustness and flexibility.
These factors play directly into the design choices behind the STT‑28.
Core product overview: STT‑28 SDI‑12 Submersible Temperature Transmitter
According to the official product page, the STT-28 SDI-12 Submersible Temperature Transmitter is:
- Designed to be permanently submersed in liquids and suspended by its cable
- Available with stainless steel or marine bronze housings for media compatibility
- Built around a highly accurate NTC thermistor, selected for accuracy and stability, with additional electronic correction for performance
- Offered in two mechanical variants:
- Standard submersible version for long-term trend monitoring where response speed is less critical
- 10 mm thin-walled probe version for very fast thermal response
- Equipped with SDI‑12 digital communications and a selection of standard and bespoke commands
- Fully submersible to IP68, suitable for permanent immersion
- Rescalable and configurable via the USB‑SDI12‑PRO – USB powered SDI‑12 interface and free Stork DCT software, using USB power from a PC or laptop
These design choices are what make it a solid option for long-term underwater work.
1. Rugged mechanical design for permanent immersion
Fully submersible, IP68 design
The STT‑28 is specified as fully submersible, IP68, allowing it to be installed permanently in tanks, estuaries, harbours and other bodies of water. IP68 indicates protection against dust ingress and continuous immersion in water under conditions specified by the manufacturer.
In practical terms for long-term monitoring:
- You can leave it in place for years without expecting failure due to normal immersion conditions.
- It is suitable for static installations where retrieving the sensor is costly or disruptive (deep tanks, offshore platforms, harbour walls, remote estuaries).
We has a strong track record in submersible devices. For example, our STT-26 Submersible Temperature Transmitter has been pressure tested to 10 bar (around 100 m water depth) in a sealed water-filled chamber to verify watertight design, making it a “fit and forget” solution for long-term temperature transmission source: STT‑26 product page. The same design philosophy clearly influences the STT‑28.
Material options: stainless steel or marine bronze
Media compatibility is a major issue for long-term submersion. The STT‑28 can be supplied in:
- Stainless steel for most freshwater, industrial and many wastewater applications
- Marine bronze for seawater, brackish water and other highly corrosive environments
This is particularly important in:
- Harbour seawater monitoring, where bronze housings resist chloride-rich seawater
- Estuary monitoring, where salinity and chemistry change dynamically
- Marine biology studies, where sensors may be mounted to fixed structures in seawater for long periods
Selecting the correct material minimises corrosion, reduces maintenance and increases confidence in data continuity.
2. High-stability sensing element and electronics
NTC thermistor selected for stability
At the heart of long-term temperature monitoring is sensor stability. The STT‑28 uses an NTC thermistor chosen for its accuracy and stability, with further correction applied in the electronics. This is crucial for multi-year deployments where even small drifts can mask genuine environmental trends.
Benefits of a well-characterised NTC plus digital correction:
- Low drift over time so that your baseline remains reliable
- Good repeatability, which is vital for trend analysis
- Ability to match sensors across networks so different installations behave consistently
This approach mirrors sensors used in demanding subsea and marine environments. For deeper or higher‑pressure applications Stork offers the SSTT Subsea Temperature Transmitter, which uses a Class A Pt100 and is rated for depths up to 3000 m with wet‑mateable connectors source: SSTT product page. While SSTT addresses high‑depth subsea use, the STT‑28 occupies the environmental / in‑liquid niche at shallower depths, still benefitting from the same emphasis on accuracy and robustness.
Optimised for long-term trend monitoring
We make a clear distinction between:
- The standard submersible STT‑28, where “temperature response is not key and trends of accurate temperature measurement over time are more important”
- The 10 mm thin-walled probe version, aimed at applications “requiring very quick response time to temperature change”
This is valuable because it lets you align the sensor variant directly with your application:
- For long-term climate or environmental monitoring, where thermal changes over minutes to hours matter, the standard version is optimised for stability and robustness.
- For fast‑changing conditions, such as rapid temperature shifts in process lines or tsunami-related studies, the thin‑walled option delivers the responsiveness needed.
Either way, you avoid compromising long-term data quality.
3. SDI‑12 digital communications for robust, low-power data
Stable SDI‑12, low power electronics
The STT‑28 uses stable, low-powered SDI-12 electronics and supports a range of standard and bespoke SDI‑12 commands to retrieve temperature data. SDI‑12 is widely used in environmental monitoring because it:
- Allows multiple sensors on a single three‑wire bus, reducing cable runs and simplifying installations
- Supports low-power operation, making it ideal for remote or solar‑powered loggers
- Provides digital output, eliminating analogue signal drift and noise issues over long cable lengths
Stork has deep expertise in SDI‑12 across their portfolio. The SLS‑D Digital Submersible Level Transmitter – SDI‑12, for example, is fully SDI‑12 Version 1.4 compliant and supports multiple sensors on a single cable with advanced calibration and density correction features source: SLS‑D product page. The same digital communication principles underpin the STT‑28.
Simple integration into existing SDI‑12 networks
Because SDI‑12 is a standard protocol, the STT‑28 can be connected to:
- Existing dataloggers and telemetry devices that already speak SDI‑12
- Mixed networks containing level and temperature devices, for example combining the STT‑28 with SLS‑D level transmitters in the same borehole or water body
- Portable USB‑SDI‑12 interfaces such as the USB‑SDI12‑PRO for local configuration and testing
This makes it a low‑risk, drop‑in option for upgrading older analogue installations or expanding current SDI‑12 monitoring schemes.
4. Easy configuration, scaling and data logging with USB‑SDI12‑PRO
A key practical aspect of long-term monitoring is how quickly you can commission, scale and troubleshoot sensors. The STT‑28 can be rescaled and configured using the USB‑SDI12‑PRO – USB powered SDI‑12 interface and free Stork DCT software:
- The USB‑SDI12‑PRO:
- The Stork DCT software lets you:
- Configure sensors and check output before installing on remote, battery- or solar-powered systems
- Data log sensors to the PC for function checks and benchmark data
- Adjust filters, sample rates and output units (pressure/level/temperature where applicable)
- Perform annual calibration adjustments in “Calibration Mode” where needed source: USB‑SDI12‑PRO product page
For the STT‑28 specifically, this means:
- You can quickly validate performance in the lab or on site before committing it to long-term deployment.
- Rescaling and unit adjustments are handled digitally, avoiding any manual potentiometer tweaks.
- Maintenance visits can include a simple USB check and recalibration if required, substantially shortening downtime.
For users already working with Stork’s SDI‑12 level instruments such as the SLS‑D, the workflow will be familiar, reducing training overhead.
5. Proven in diverse real‑world applications
The STT‑28 is used in a wide variety of underwater and in‑liquid temperature monitoring roles, as highlighted on its product page:
- Water tank temperature measurement
For domestic and industrial tanks, the sensor is submerged in the tank and suspended by its cable to provide real‑time, accurate temperature readings. This supports:- Energy optimisation in heating systems
- Process quality control in industrial storage
- Early detection of unexpected thermal events
- Legionella prevention systems
Continuous temperature monitoring in hot and cold water systems is essential to prevent Legionella growth. The STT‑28 provides continuous trend data, helping facilities:- Maintain temperatures outside Legionella growth ranges
- Demonstrate compliance with regulations and risk management plans
- Tsunami and disturbance monitoring
Rapid changes in water temperature can be a proxy for underwater disturbances and can support wider seismic monitoring systems. Here the fast‑response 10 mm thin-walled probe variant offers:- Rapid reaction to thermal fronts or upwellings
- Integration into multi‑parameter coastal monitoring networks
- Harbour seawater monitoring
In harbours, the STT‑28 in marine bronze housing provides:- Continuous seawater temperature trends for environmental and operational decisions
- Data that can be correlated with industrial activity, run‑off events or seasonal variations
- Inputs for public information (for example swimming conditions) and ecological studies
- Estuary temperature analysis
Estuaries see constant mixing of fresh and saltwater, with resulting thermal gradients. Long‑term temperature records are critical for:- Understanding habitat conditions for fish and invertebrates
- Managing fisheries and nursery grounds
- Assessing climate change impacts on estuarine systems
- Environmental monitoring systems generally
From rivers and reservoirs to constructed wetlands, the STT‑28 provides the temperature component in broader monitoring suites that may also track level, flow, conductivity and quality. - Marine biology and oceanographic studies
Long-term temperature profiles underpin research into species distribution, behaviour and ecosystem responses to warming. The STT‑28’s accuracy plus stability make it a strong candidate for such studies at shallow to medium depths, particularly in coastal and near-shore environments.
These applications highlight why a robust, low-drift, SDI‑12 enabled device is needed instead of a basic, low‑cost temperature probe.
6. Integration with wider Stork Solutions ecosystem
Choosing a device like the STT‑28 is often part of a wider instrumentation strategy. One of the advantages of sourcing from Stork Solutions is the consistent philosophy across their range:
- Temperature transmitters family
In addition to the STT‑28, the Temperature Transmitters range covers:- Submersible, subsea and in‑line temperature devices
- Marine approved and high‑pressure solutions such as the SSTT Subsea Temperature Transmitter
- Other submersible options like the STT‑26
- Level and environmental measurement
For combined level and temperature in submersible applications, the SLS‑D Digital Submersible Level Transmitter – SDI‑12 offers:- Fully verified SDI‑12 v1.4 compliance
- Low power consumption
- High‑integrity overmoulded cable assemblies
- Level and temperature output as standard
- Accessories and configuration tools
The USB‑SDI12‑PRO and associated Stork DCT software underpin the configuration, calibration and data logging strategy for both level and temperature devices, simplifying fleet management.
For end users, this means:
- A consistent approach to communications, power, configuration and documentation
- Easier multi-sensor system design, whether building an environmental monitoring station, flood defence telemetry point, or research installation
- A single technical partner for both temperature and level instrumentation
7. Key reasons the STT‑28 is a reliable long-term choice
To summarise, the STT‑28 SDI‑12 Submersible Temperature Transmitter is a strong candidate for long-term underwater temperature monitoring because it offers:
- Mechanical robustness for permanent immersion
- IP68 fully submersible design
- Purpose-built to be suspended by its cable in tanks, rivers, estuaries and coastal waters
- Media compatibility and corrosion resistance
- Choice of stainless steel or marine bronze housings to match freshwater, seawater and industrial liquids
- High accuracy and low drift sensing
- Carefully selected NTC thermistor with electronic correction
- Designed for long-term trend reliability where absolute stability matters
- Configurable response dynamics
- Standard version for long-term trend monitoring
- Thin-walled 10 mm probe for rapid response applications
- Robust SDI‑12 digital communications
- Stable, low-power SDI‑12 electronics for remote, battery or solar-powered systems
- Multi-sensor bus capability and digital data integrity over long cable runs
- Simple configuration, scaling and data logging
- Works seamlessly with USB‑SDI12‑PRO and Stork DCT software
- Up to 10 SDI‑12 devices can be managed and logged simultaneously from a laptop
- Proven across demanding applications
- Used in water tanks, Legionella prevention, tsunami-related monitoring, harbour and estuary studies, environmental and marine biology applications as detailed on the product page
- Integration with a broader ecosystem
- Fits alongside Stork’s temperature transmitters and submersible level transmitters, simplifying system design and support
For any project that requires robust, accurate and low‑maintenance temperature data over the long term, particularly in environmental and coastal contexts, the STT‑28 SDI‑12 Submersible Temperature Transmitter offers a compelling balance of mechanical reliability, measurement stability and digital integration.
