Sensors 1 Flashcards
What is a sensor?
Transforms a stimulus into a measurable signal, converted into a measurable output.
What are the ways in which sensors can be classified?
Physical phenomena (mech, thermal, optical, chemical)
Measuring Mechanism (resistance, capacitance, inductance)
Sensor placement (contact, non contact)
Power Supply (Passive - no power source, Active - requires power)
What are the sensor specifications?
Calibration
Sensitivity
Linearity
Hysteresis
Environmental Effects
Accuracy
Precision
Measurement errors
Threshold
Range(span)
Resolution
Describe sensor calibration.
Comparison of sensor output with known measurement system.
Describe sensor sensitivity.
The change of sensor output for a unit change of input.
E.g thermocouple, sensitivity = change in V / change in temp (gradient)
Describe sensor Linearity.
A sensor is linear if the output is linearly proportional to the input. ( a good thing)
Describe sensor hysteresis.
For a given input, the output from the sensor varies depeneding on whether the input stimulus is increasing or decreasing at the time.
Given as a %
Max hysteresis = ((max difference of voltage)/ max voltage) * 100
Describe sensitivity drift.
How close the measured output is to the true input value.
Describe precision.
How repeatable the measurement
What are the two types of measurement errors?
System errors - imperfect design of measurement setup
Random errors - uncontrolled variables (reduce by averaging)
What is sensor threshold?
Smallest input that will produce a reading
What is sensor range?
Min and max readable
What is sensor resolution?
Smallest change in input that will produce detectable change.
What is the equation for Voltage relating to resistance?
Voltage = Vtotal * Rf / Rs
Capacitance Equation
Capacitence = A * e / d
