Roboticsinfo
From WikIRI
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Robotics Information
Sensor
Sensor Performance
Characteristics of sensors which can affect your results and recommendations on how to lessen their effects.
REPEATABILITY
Repeatability is the ability of the sensor to respond in the same way to a repeatedly applied force. As with most measurement devices, it is customary to exercise, or "condition" a sensor before calibrating it, by loading it to 110% of the test weight four or five times. (See Conditioning Sensors)
LINEARITY
Linearity refers to the sensor’s response relation digital output to the applied load, over the range of the sensor. This response should ideally be linear; and any non-linearity of the sensor is the amount that its output deviates from this line.
HYSTERESIS
Hysteresis is the difference in the sensor output response during loading and unloading, at the same force. For static forces, and applications in which force is only increased, and not decreased, the effects of hysteresis are minimal. If an application includes load decreases, as well as increases, there may be error introduced by hysteresis that is not accounted for by calibration.
DRIFT
Drift is the change in sensor output when a constant force is applied over a period of time. If the sensor is kept under a constant load, the resistance of the sensor will continually decrease, and the output will gradually increase. It is important to take drift into account when calibrating the sensor, so that its effects can be minimized. The simplest way to accomplish this is to perform the sensor calibration in a time frame similar to that which will be used in the application.
TEMPERATURE SENSITIVITY
In general, your results will vary if you combine high loads on the sensor with high temperatures. To ensure accuracy, calibrate the sensor at the temperature at which it will be used in the application. If the sensor is being used at different temperatures, perform a calibration at each of these temperatures, save the calibration files, then load the appropriate calibration file when using the sensor at that temperature.
SENSOR LIFE / DURABILITY
Sensor life depends on the application in which it is used. load cycles using a 50 lb. force. Rough handling of a sensor will also shorten its useful life. It is also important to keep the sensing area of the sensor clean. Any deposits on this area will create uneven loading, and will cause saturation to occur at lower applied forces.
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