Deadweight Calibrating Machine

With accuracies of better than 0.002 % of the applied force, the Morehouse Deadweight Calibrating Machine is the most accurate force standard. It is ideal for those concerned with measurement risk and maintaining a better than 4:1 Test Uncertainty Ratio (TUR) on the force-measuring instruments with a tolerance of 0.05 % or better.

All Morehouse Deadweight Calibrating Machines make full use of the accuracy of deadweights and are true primary standards. This means there are no multipliers (hydraulic or otherwise), levers, or flexures between the weights of the calibrator and the instrument to be calibrated.

Deadweight Calibration Machine Capability

Morehouse deadweight machines are capable of calibrating ISO 376 Class 00, ASTM E74 Class AA, AS 2193 Class AA, and other force-measuring devices requiring the utmost accuracy. These include load cells, proving rings, crane scales, force gages, dynamometers, and other force-measuring devices.

Morehouse has redesigned our deadweight calibrating machine to be more rigid, have more room between weights, have conical lifters so low-pressure air bladders can lower the weights to eliminate shock loading, and use new designs to ensure the yoke will not twist apart. The new automated control features a programmable controller where a touch screen is used for manual mode. The end-user can set timing and loading sequences, including data capture, so that all data can easily be exported to your current calibration software, or the machine's USB communication port can be used to work with LabVIEW and other programs.

Design Highlights:

  • Clean operation with around 15 PSI air pressure when the airbags are deflated and inflated steadily to eliminate shock load.
  • The controller is set up for manual touchscreen operation for calibration of instruments without data capture capabilities.
  • Automation routines are easy to program, and timing profiles can be set to ensure compliance with ISO 376, which states in section 7.4.3 "The time interval between two successive loadings shall be as uniform as possible, and no reading shall be taken within 30 s of the start of the force change."
  • The yoke is designed to eliminate twisting and unthreading during operation, a common problem with most machines because threads want to unthread over time.
  • Everything is engineered with at least a 2:1 safety factor. It is impossible to overload a deadweight machine, but the overall design is good for over 1,000,000 full capacity or more loadings.
  • Each level of the machine has room to allow each weight to clear and for deflection of the unit being calibrated. The weights will not touch the top or bottom supports when hanging. Other machines may not have an adequate gap or spacing, which results in a weight resting and the proper force is not applied.
  • The loading surfaces are designed to minimize bending and accept various-sized force-measuring instruments.
  • All weights are designed with corrosive-resistant material or Stainless steel, depending on the budget. The weights are designed to be stable over a decade of use to 0.2 ppm.
  • Tension and compression loading is easy with a ball seat in the yoke frame and quick-change tension adapters.
  • Designed to calibrate load cells with a tight tolerance of 0.005 % or better. It is the only standard capable of assigning ASTM Class AA verified range of forces and the preferred machine for ISO 376 Class 00 calibrations.


Deadweight machines start at $70,000.00 USD.

Pricing is often dependent on the size of the machine, cost of calibration of the weights, material of weights, number of weights, engineering costs, and freight. Typical pricing is around $25.00 - $50.00 per lbf for higher-capacity machines. When the accuracy of deadweight is not required, our Morehouse Universal Calibrating Machine, with accuracies of better than 0.02 % of applied, may be an acceptable alternative. The UCM machines of 100K and under range from $20 - $50K, depending on options.


All weights are adjusted to better than 0.002 % of their nominal value. They are calibrated and certified either directly traceable to SI units through an ISO/IEC 17025 accredited lab or directly by the United States National Institute of Standards and Technology (NIST).

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