Should I order a calibrated sensor?
Standard uncalibrated sensors are somewhat non-linear and hence the relationship of applied force against output does not follow a straight line and in fact is curved (Left Image). Furthermore, a standard sensor’s full-scale output is only approximately in-line with the full-scale load.
Calibrating the sensor linearizes the output and ensures that the full-scale output matches full-scale input with a maximum deviation of 2%. See example below (Right Image).
Advantages of calibration:
- Linear output curve
- Higher accuracy
Disadvantages of calibration:
- Calibration requires the electronics to be, and remain matched to the sensor for the duration of use. Therefore electronics and sensors can no longer be swapped. This is due to the calibration data being stored in the electronics’ on-board flash memory. If the sensor is damaged, the electronics has no future use.
- Cost – A calibrated sensor costs an additional $25 over a standard sensor.
Calibrated system (Sensor + Electronics) = $75,
Standard sensor = $20 + electronics ($30) = $50.
Calibration does not significantly affect:
- Repeatability – both sensors are repeatable (it is just that the calibrated one gives an output value closer to the true value).
- Sensitivity or Signal to Noise Ratio (SNR)
- Hysteresis
- Drift. Where output signal slowly increases and is independent of the applied force, typically due to temperature variations or material creep – SingleTact creep is less than 2%.
- Response time
When would you desire calibration?
- When accuracy and linearity are a main driver – calibrated sensors have improved linearity and accuracy. An instrumentation application example is where the output result should be accurate to 2%.
Cases where you should consider a standard sensor
- Where an accuracy of 10% is satisfactory. An example application example is when using the sensor as a thin film button.
- If you are considering performing your own calibration method.
- If cost is the main driver.
- If you want to use a single set of electronics to evaluate multiple sensors configurations.
