In the deployment of oceanographic instruments, knowing the weight of an instrument in water is essential for designing effective underwater rigs and buoys. The buoyancy characteristics play a crucial role in determining how these instruments behave when submerged.

Buoyancy, a well-known force in fluid dynamics, is the upward force exerted by a fluid (such as water) on an object submerged in it. According to Archimedes' Principle, this buoyant force is equal to the weight of the fluid displaced by the object. The apparent immersed weight of an object in water can be calculated using the formula:

Apparent immersed weight=weight of object−weight of displaced fluid

Here, the weight of the displaced fluid is constant and depends on the volume of the object submerged. This remains consistent even when the object's contents (such as batteries) change. In the context of determining buoyancy for instrument deployment, the primary task involves straightforward addition and subtraction to account for changes in the object's weight when submerged. Understanding these principles is fundamental for optimizing the design and performance of underwater equipment.

For detailed buoyancy data, visit our website. Under "Products," locate your specific instrument, and under "Technical Documents" or "Technical Drawings," you'll find a general assembly drawing containing all the necessary information for buoyancy calculations. Due to the variety of battery combinations available, we only specify the weight of the instrument itself. To determine the total instrument weight with additional batteries, simply add the weight of the chosen battery option. For specific battery weight information, refer to our website under "Products" and "Spare Parts."

If weight details are not provided on the drawing, please reach out to Nortek Support for assistance.

Example calculations

Signature 500 with Standard Housing and 180Wh Battery:

• • Weight in Air:
    • Weight of Signature 500 (standard housing, no battery): 6.4 kg
    • Weight of 180Wh battery: 1.8 kg
    • Total weight in air: 6.4 kg + 1.8 kg = 8.2 kg
  • Weight in Water:
    • Weight of Signature 500 (standard housing, no battery): -0.3 kg
    • Weight of 180Wh battery: 1.8 kg
    • Total weight in water: -0.3 kg + 1.8 kg = 1.5 kg

Signature 500 with Long housing and 540Wh Battery:

• • Weight in Air:
    • Weight of Signature 500 (long housing, no battery): 8.6 kg
    • Weight of 540Wh battery: 5.1 kg
    • Total weight in air: 8.6 kg + 5.1 kg = 13.7 kg
  • Weight in Water:
    • Weight of Signature 500 (long housing, no battery): -2.5 kg
    • Weight of 540Wh battery: 5.1 kg
    • Total weight in water: -2.5 kg + 5.1 kg = 2.6 kg