Sensors

Signals

Represent a physical/chemical quantity we want to measure them or use them to interact with a patient

Transducers

Convert signals between different physical forms
Sensors - from non-electrical to electrical
Actuators - from electrical to non-electrical

The signal chain

Sensor > pre-amplifier > cables > amplifier > ADC

Resolution

Smallest change of input parameter that can be reliably detected on output signal. Typically determined by noise

Nonlinearity

Deviation from ideal linear dependence between input and output

Ideal line

End to end or least squared, check which definition manufacturer is using

Hysteresis

Value of measured parameter differs depending on direction of change of parameter

Response time

Time required for the output to change from its previous value to a final settled value within a given tolerance band

Sensor errors

Characteristic, dynamic, environmental

Accuracy

Closeness to true value

Precision

Closeness of multiple observations

Offset error

Sensor output measured when 0 output would be expected

Bias error

Difference between measured average and true value

Sensitivity error

Error caused by the fact we don’t know the sensitivity