There are different types of sensors that produce continuous analog output signal and these sensors are considered as analog sensors. This continuous output signal produced by the analog sensors is proportional to the measurand. There are various types of analog sensors; practical examples of various types of analog sensors are as follows: accelerometers, pressure sensors, light sensors, sound sensors, temperature sensors, and so on.
Accelerometers
Analog sensors that detect changes in position, velocity, orientation, shock, vibration, and tilt by sensing motion are called as accelerometers. These analog accelerometers are again classified into different types based on the variety of configurations and sensitivities.
These accelerometers are available as analog and digital sensors, based on the output signal. Analog accelerometer produces a constant variable voltage based on the amount of acceleration applied to the accelerometer.
Light Sensors
Analog sensors that are used for detecting the amount of light striking the sensors are called as light sensors. These analog light sensors are again classified into various types such as photo-resistor, Cadmium Sulfide (CdS), and, photocell. Light dependent resistor (LDR) can be used as analog light sensor which can be used to switch on and off loads automatically based on the day light incident on the LDR. The resistance of the LDR increases with decrease in light and decreases with increase in light.
Sound Sensors
Analog sensors that are used to sense sound level are called as sound sensors. These analog sound sensors translate the amplitude of the acoustic volume of the sound into an electrical voltage for sensing sound level. This process requires some circuitry, and utilizes microcontroller along with a microphone for creating an analog output signal.
Pressure Sensor
The analog sensors that are used to measure the amount of pressure applied to a sensor are called as analog pressure sensors. Pressure sensor will produce an analog output signal that is proportional to the amount of applied pressure. These pressure sensors are used for different types of applications such as piezoelectric plates or piezoelectric sensors that are used for the generation of electric charge. These piezoelectric sensors are one type of pressure sensors that can produce an analog output voltage signal proportional to the pressure applied to the piezoelectric sensor.
Analog Temperature Sensor
Temperature sensors are widely available as both digital and analog sensors. Typically used analog temperature sensors are thermistors. There are different types of thermistors that are used for different applications. Thermistor is a thermally sensitive resistor that is used for detecting changes in temperature. If the temperature increases, then the electrical resistance of thermistor increases. Similarly, if temperature decreases, then the resistance decreases. It is used in various temperature sensor applications.
Practical example of analog temperature sensor is thermistor based temperature control system. This project is used to maintain constant temperature in an enclosed area. A block diagram of temperature control system consists of lamp(that represents a cooler), temperature sensor or thermistor, relay.
If the temperature exceeds certain value, then the lamp switches on automatically indicating a cooler for bringing back temperature to normal value. Operational along with a negative temperature coefficient thermistor is used for activating relay-in case if the temperature exceeds certain range. As this process of activating relay for switching on cooler (in this system shown as lamp) can be done automatically, hence there is no need to monitor temperature in person. Thermistoris most frequently used analog temperature sensor, because of its low cost advantage. Whenever changes occur in temperature, then the input parameters to the op-amp will be altered. Thus, op-amp delivers an output that energizes relay and the load turns on or off accordingly.
If we use a digital temperature sensor instead of analog temperature sensor, then the accuracy of temperature control system can be improved.