A lab in a top secret facility in Baltimore, USA, is analysing a new nerve gas. A sample is currently spinning above an electrosonic accelerating piston inside a super-secure glass chamber.
The lab uses a monitoring and control system just in case the special chamber's glass casing breaks.
It uses a gas sensor which is pretty dumb. It just collects and sends analogue data to a microprocessor.
Microprocessors have a problem with this - they only understand digital data. So, an analog-to-digital converter is required - see the red box.
What would happen if the glass broke? Let's find out! GET THE HAMMER!
So how does this work?
How does the computer know that the data coming from the sensor, after being converted to digital, represents a dangerous situation?
How does it turn on the alarm?
Reorder the steps taken by the control system so that it works as expected.
Other common sensors include:
Some sensor systems use transducers. Transducers convert energy from one form to another.
For example, a heater might transform electricity to heat.
An actuator is a specific type of transducer. It transforms electrical energy into movement/motion.
For example, an automatic door would use an actuator to open the door when someone is sensed nearby.
Note, analogue and digital signals are quite different:
Common scenario 1
An automatic door is closed. Analogue data sent to a microprocessor by a motion sensor is converted to digital data by an ADC.
The digital data received by the microprocessor is compared to a stored value and the result is that nothing happens.
You walk towards the door. The microprocessor is still receiving data and making comparisons with stored data. The data received is now greater than the stored value and the microprocessor sends a signal to an actuator to open the door.