Sensors Flashcards
What is the definition of a sensor?
A device whose purpose is to detect events or changes in an environment and send that data to other electronics. Sensors are always used with other electronics.
What is the resolution of a sensor?
It is the minimum change that can be detected in the quantity that is being measured.
What is the range of a sensor?
It is the operating range of a sensor, or the max and min values that it is able to read. Magnetic fields and optical position sensors have small ranges but infrared and sonar have large ranges.
What is the difference between an absolute and incremental sensor?
An absolute sensor will measure a unique value, but an incremental sensor will measure a value that depends on the previous value.
What is analogue sensor measurement?
Analog sensors will output a signal that is proportional to the quantity that they are measuring. The relationship between the output signal and the actual measurement depends on the type of sensor.
What are the three sensor responses?
Linear, exponential and polynomial.
How do we model a linear sensor?
Using y = ax + b, where a is the rate of change and b is the offset. x is the output of the sensor and y is the measurement.
What are the models for polynomial and exponential sensors?
y = ax^2 + bx + c y = ae^bx
What is a pressure sensor?
It will perform a pressure measurement of a gas or a liquid. The voltage signal generated is proportional to the amount of pressure. We can also use them to indirectly measure other values, like the volume of fluid in a reservoir.
What is a potentiometer?
It is an absolute analog sensor that is used to measure angular position. Signal is discontinuous because after a few revolutions there signal will be reset to zero. It is a circle of wire with a rotor in the middle, based on the rotor position it will effect the resistance and therefore the output voltage
What is an InfraRed Sensor?
It is typically composed of an IR emitting diode, a positioning sensor diode and then a signal processing unit. It outputs a voltage that correlates to the distance of the remote target. They have a smaller range than sonar but a better resolution.
What is a Sonar Sensor?
It is an emitter that emits ultrasonic waves and a receiver that captures them after hitting a target. They use a timer to calculate how long it takes for the waves to return. Good for long distance measurement.
What is an Optical Position Sensor?
They are used in robotics and machine automation. they use an IR emitting diode along with a NPN phototransistor to measure the position of a target.
What is a transducer and how is it related to a sensor?
It is a device that is used to convert energy from one form to another, or a signal from one form to the other. A sensor is a type of transducer that produces a signal that represents information about the environment that it is in. However, a measurement may use both a transducer and a signal in the same circuit.
What is a smart sensor and what can it do
It is a sensor and a signal conditioning circuit packaged to together with a microcontroller. This means that it is able to account and compensate for random errors, and to adapt to changes in the environment. It is able to calculate its accuracy, convert non linearities into a linear outpu and self and self diagnose.
