Combined Temperature and Water Level Measurement
The Rosemount 765 is a tank gauging sensor designed to provide two important measurements from one integrated assembly: liquid temperature at multiple heights and free water level at the bottom of the tank.
Multiple Pt-100 elements are installed at different heights to create a vertical temperature profile. Fully immersed elements are used to determine product temperature, while one temperature element can be positioned inside the water level probe for temperature measurement close to the tank bottom.
The integrated water level sensor detects the interface between the stored product and free water that settles at the bottom of the tank. This information can be used together with level and temperature measurements to improve product volume calculations.
Up to 16 Pt-100 Temperature Measurement Points
Depending on the selected configuration, the Rosemount 765 supports 10, 14 or 16 temperature spot elements.
The Pt-100 elements are distributed along the sensor at specified heights, allowing operators to monitor temperature distribution throughout the tank rather than relying on a single measurement point.
This multi-point temperature profile is particularly useful for tank inventory calculations where accurate average product temperature is required.
Integrated Free Water Level Measurement
The major advantage of the Rosemount 765 compared with a conventional multiple spot temperature sensor is its integrated water level measurement.
The capacitive water level sensor is available with:
- 500 mm active measuring range
- 1000 mm active measuring range
- ±2 mm level accuracy for the 500 mm version
- ±4 mm level accuracy for the 1000 mm version
- ±0.5 mm repeatability
Two sensor designs are available:
- Open model: Recommended for crude oil and heavy-duty products
- Closed model: Recommended for lighter products such as diesel oil
Designed for Accurate Tank Inventory Calculations
The Rosemount 765 is intended for applications where temperature and free water measurements affect the calculated quantity of stored product.
The temperature measurements and water level information are transmitted through the Rosemount 2240S Multi-input Temperature Transmitter. The data can then be integrated into the Rosemount tank gauging system, TankMaster inventory software, or a DCS/host system.
Reliable Construction for Storage Tanks
The Rosemount 765 uses a stainless steel AISI 316 protective sheath with a 1-inch diameter. The sensor is designed as a heavy-duty assembly with no moving parts, and the water level sensor is hermetically integrated with the temperature sensor tube.
The sensor can be anchored to the tank bottom to maintain a fixed position, particularly where turbulence may affect the sensor position.
High-Accuracy Temperature Measurement
The Rosemount 765 uses Pt-100 spot elements according to IEC 60751:2022.
Available thermometer tolerance options include:
- 1/10 B-sp: ±(0.3 + 0.005 |t|) °C
- 1/6 B-sp: ±(0.3 + 0.005 |t|) °C
- Optional Callendar-Van Dusen calibration: ±20 mK uncertainty under the specified calibration conditions
The calibrated option can significantly improve overall temperature measurement performance for demanding inventory and custody-transfer applications.
Key Technical Highlights
- Sensor type: Multiple spot temperature and water level sensor
- Temperature element: Pt-100
- Number of temperature elements: 10, 14 or 16
- Temperature element standard: IEC 60751:2022
- Temperature range: 0 to +120 °C for Rosemount 765
- Thermometer accuracy: 1/10 B-sp or 1/6 B-sp
- Optional calibrated uncertainty: ±20 mK with applicable X8 calibration
- Water level measuring principle: Capacitive
- Water level active range: 500 mm or 1000 mm
- Water level accuracy: ±2 mm / ±4 mm
- Water level repeatability: ±0.5 mm
- Overall length: 2–60 m
- Protective sheath: AISI 316 stainless steel
- Sheath diameter: 1 in.
- Mounting thread: M33 × 1.5
- Minimum tank opening: 2 in. (50.8 mm)
- Water level sensor diameter: 38 mm closed / 48 mm open
- Communication: High-speed RS485 / Modbus via Rosemount 2240S
- Protection: IP68 when connected to Rosemount 2240S
- Compatible transmitter: Rosemount 2240S Multi-input Temperature Transmitter
Typical Applications
Bulk Liquid Storage Tanks
The Rosemount 765 is designed for bulk liquid storage where accurate temperature and water level information are required for inventory calculations.
Crude Oil Storage
The open water level sensor is recommended for crude oil and heavy-duty products, providing free water measurement near the tank bottom.
Diesel and Light Fuel Storage
The closed water level sensor is recommended for lighter fuels such as diesel oil.
Tank Inventory Management
The combination of temperature profiling, water level measurement and tank level information helps improve calculated product volume and inventory accuracy.
Custody Transfer
Four-wire multiple spot temperature measurement and optional sensor calibration support applications requiring accurate net standard volume calculations. Emerson specifically positions the Rosemount 765 for custody-transfer-related tank measurement.
Frequently Asked Questions
What is the Rosemount 765 used for?
The Rosemount 765 is used for multi-point temperature measurement and free water level detection in bulk liquid storage tanks. It supports accurate inventory and net volume calculations.
How many temperature points can the Rosemount 765 measure?
The Rosemount 765 can be configured with 10, 14 or 16 Pt-100 temperature spot elements, depending on the selected wiring and configuration.
What type of temperature sensor does Rosemount 765 use?
The Rosemount 765 uses Pt-100 spot elements according to IEC 60751:2022.
What is the water level measurement range?
The integrated water level sensor is available with an active measuring range of 500 mm or 1000 mm.
What is the accuracy of the Rosemount 765 water level sensor?
The water level accuracy is:
±2 mm for the 500 mm active range
±4 mm for the 1000 mm active range
Repeatability is ±0.5 mm.
What is the temperature accuracy of Rosemount 765?
The Pt-100 temperature elements are available with 1/10 B-sp or 1/6 B-sp tolerance. The specified tolerance is ±(0.3 + 0.005 |t|) °C according to IEC 60751. An optional Callendar-Van Dusen calibration can provide ±20 mK uncertainty under the specified conditions.
What is the temperature range of Rosemount 765?
The Rosemount 765 has a specified temperature range of 0 to +120 °C (32 to +250 °F).
What is the difference between Rosemount 765 and Rosemount 565?
Both are multiple spot temperature sensors for tank measurement, but the Rosemount 765 additionally includes an integrated water level sensor.
Rosemount 565 → Multiple spot temperature measurement
Rosemount 765 → Multiple spot temperature + free water level measurement
What is the difference between Rosemount 765 and Rosemount 566?
The Rosemount 765 is designed for bulk liquid storage tanks and combines temperature profiling with water level measurement.
The Rosemount 566 is designed for cryogenic and refrigerated storage applications such as LNG, using Class A Pt-100 elements for low-temperature measurement.
What transmitter is used with Rosemount 765?
The Rosemount 765 is connected to the Rosemount 2240S Multi-input Temperature Transmitter, which receives the temperature and water level measurements.
Is Rosemount 765 suitable for crude oil?
Yes. The open water level sensor version is specifically recommended for crude oil and heavy-duty products.
Is Rosemount 765 suitable for diesel?
Yes. The closed water level sensor version is recommended for lighter products such as diesel oil.
