Temperature Considerations

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FARO was awarded the U.S. patent #5,402,582, and worldwide patents are pending, on the concept and the methods for temperature compensation of portable CMM devices. This brief overview is meant only as the most general of descriptions.

To maintain certified accuracy in a multitude of environments, the monitoring of temperature and the rate of temperature change is required. Only the ScanArm employs a software/hardware solution where a semiconductor temperature sensor is built into each joint.

The temperature is continuously monitored and the difference over time is then applied to the mathematical formulas or kinematics, which define the position of the ScanArm in three-dimensional space. Link length corrections are made constantly by the inboard processor, which adjusts the kinematics and constantly adapts the output to changing environmental temperature.

However, because different components heat or cool at different rates, the device is expected to reach a steady state temperature within a ±3 degree (Celsius) bandwidth for five minutes before measurements can be taken. For convenience, the electronics system is programmed to generate an error message when the temperature exceeds a ±3 degree bandwidth. There is also a built-in routine for the establishment of temperature stability; whereby, the device monitors itself for five minutes and indicates to the user that it is ready for use.