FBD Dynamometer Series

Product Details

The Force Balance Dynamometer (FBD) Series is for use in vacuum and temperature chambers which measure both static unbalance (due to CG offset) and dynamic unbalance (due to product of inertia) and eliminates errors due to aerodynamic forces. When measuring static and dynamic unbalance of a satellite in a vacuum chamber to balancing inertia wheels, the FBD series of force balance dynamometers offers a high accuracy solution for demanding applications. System software collects unbalance data, reports unbalance information, calculates correction mass solutions, and measures the expected residual unbalance of the payload after balancing.

This new instrument has the ability to spin balance a payload in a vacuum environment and thereby provide a solution to eliminate errors due to aerodynamic forces. It is low profile, permanently calibrated, has unmatched sensitivity, and can be used over a wide temperature range. Measurement sensitivity of the FBD system is equivalent to the Space Electronics traditional POI series, which features the best accuracy in the world for low spin speed applications.

Our force balance dynamometers use a unique design that provides key advantages:

  • Static and Dynamic Balancing: The FBD instrument measures center of gravity and product of inertia simultaneously. Static balancing along two axes and dynamic balancing in two planes can be performed simultaneously.
  • Vacuum Compatibility: Our FBD can be made in vacuum compatible versions for use in a vacuum chamber. This allows measurement of spacecraft or other objects without air drag. In particular the FBD series do not use any air or oil for operation.
  • Large Thermal Range: The FBD series can be calibrated and used over a wide range of temperatures, for measurement of spacecraft balance at different temperature points.
  • Compact height: The FBD series have been designed with reduced height (less than 12 inches / 30 cm for the large FBD2200) to take minimum space in a vacuum or thermal chamber. This maximizes the dimensions of the payload that can be tested in the chamber.
  • High Measurement Sensitivity: FBD instruments have the same sensitivity as our POI series which feature the best accuracy in the world for low spin speed balancing.

Typical Payloads

  • Satellites (spinning about their own bearings)
  • Satellites (non-spinning)
  • Inertia Wheels

General Technical Specifications

Maximum Payload Mass20 lb200 lb2,200 lb
Range of Spin Speeds0 – 40 RPM50 – 200 RPM30 – 150 RPM
Minimum Achievable Readout0.01 lb-in2 at 30 rpm0.07 lb-in2 at 50 rpm
0.01 lb-in2 at 100 rpm
0.003 lb-in2 at 200 rpm
2 lb-in2 at 30 rpm
0.5 lb-in2 at 50 rpm
0.15 lb-in2 at 100 rpm
Unbalance-Reduction Ratio95%85%85%


Product Sheets

Click to download the FB Dynamometer flyer.

Design Features

The FBD instrument is designed for use in vacuum chambers and temperature chambers. It is designed specifically to be low profile, measuring less than one foot in height, so that the whole instrument can be placed in a chamber. This overcomes limitations of hook height or test chamber space.

This is a major design enhancement over previous designs that use oil or compressed air. With those previous designs, the interface between the instrument and the chamber was problematic.
Instrument Selection FBD instruments can be delivered with or without a spin motor. The version without a motor is used by test engineers to balance payloads that spin about their own bearings,
eliminating the time-consuming process of precisely aligning the payload spin axis with the rotation axis of a spin balance machine.

The payload can be balanced without separating its rotating and non-rotating portions, which allows balancing or balance verification at any point in the integration and test flow without violating the integrity of a fully tested structure. Typical applications include spacecraft and inertia wheels.

Space Electronics currently offers two capacity ranges of the FBD instrument: a tabletop, 200 lb capacity instrument that can be used to balance payloads as small as 2 lb CubeSats, and a 2,200 lb capacity version used to balance full-size spacecraft.

Plans for future development include a smaller version to balance lightweight payloads such as inertia wheels, as well as a large capacity version to balance payloads weighing as much as 22,000 lb.

Product of Inertia (POI)


Point of Inertia Spin Balance
POI Spin Balance Series View Product

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