FSD (Full Scale Deflection): Understanding Sensor Range Limits
Full scale deflection is the maximum input value an instrument or sensor is calibrated to measure within its specified range. At full scale deflection, the device output reaches its full scale output for that range.
What Does Full Scale Deflection Refer to?
- Range limit: the upper end of the calibrated measurement range, for example 0 to 100 Nm.
- Corresponding output: the maximum stated output signal at that input, such as 10 V, 4 to 20 mA, or full digital counts.
How does Full Scale Deflection relate to Torque Sensors?
For many torque transducers, full scale deflection corresponds to a defined elastic twist of the shaft at the rated torque. Staying within full scale deflection helps ensure the shaft remains within its elastic operating region, supporting repeatable measurements.
How is Full Scale Deflection Used in Specifications?
Many performance figures are expressed as a percentage of FS or FSD, for example when looking at Datum Electronics 425 Series Torque Transducers:
- Accuracy Class: 0.1
- Non-linearity: ±0.1% FSD
- Hysteresis and Repeatability: ±0.05% FSD
Important Notes
- FSD describes capacity, not uncertainty. It is not the same as measurement noise, standard deviation, or measurement uncertainty.
- Exceeding FSD may result in poor readings from reduced accuracy, or even permanent mechanical damage.
Related Terms
- Full scale range (FSR): the span from minimum to maximum value, including negative to positive ranges where applicable.
- Rated output: the output signal at full scale deflection.
- Rated Load: the maximum load or force that a device is designed to measure or withstand under specified operating conditions.
- Overload capacity: the maximum permissible input beyond full scale deflection before damage or specification loss is expected.