Topic 8: Monitoring, measurement and control technology Flashcards
What is datalogging and what are the main features?
Datalogging is where readings are taken regularly over a period of time using sensors. The main features of datalogging are:
What are some examples of sensors?
What are the advantages and disadvantages of datalogging?
Advantages:
What are actuators?
Actuator is a mechanism that causes a device to be turned on or off, adjusted or moved. An actuator therefore produces some form of movement according to a signal sent to it by the computer. Actuators are needed to turn taps on/off, alter valves, open by different amounts, etc.
What sensors do touchscreens use?
Touch/tactile sensors.
What are the main components of a control system?
What are non-feedback control systems?
If you are writing a simple program to control a robot arm by rotating it, you can issue instructions to the stepper motor. A stepper motor rotates in shot steps and you can determine how many steps you need. This will determine the angle it moves through. The motor will rotate through an angle and then stop. This is a non-feedback system because there is no way of detecting whether it is actually moved through the correct angle. If there was an obstacle in the way of the arm, it may not have been able to move through the correct angle. If another instruction was issued then it will simply move from its incorrect starting point.
What are the aims of traffic control systems?
What are stepper motors?
A motor that turns in a series of small steps. The control signals tell the stepper motor how many steps and in which direction it should move. You can therefore control the angle through which the motor rotates. Stepper motors are found in robot arms.
What are bells/sirens?
These are used in control systems were an alarm signal needs to be sounded. Burglar alarms use bells/sirens.
What are heaters/coolers?
These are used for controlling the temperature of an environment. Central heating/air conditioning systems use heaters/coolers as their output device.
How do control systems work?
Input bits (0’s and 1’s) are detected by the sensors. For example, the imputs bit for a temperature sensor might be set to 1 if the temperature is too high. Otherwise it would be set to 0. Output bits (0’s and 1’s) control output devices. For example, if an output bit is set to 1, the heater would be turned on and if it is 0 it would be switched off. The control program deals with the input bits and applies rules to it in order to set each of the output bits.
What is analogue to digital conversation?
Analogue quantities are continuously variable, which means that they do not jump in steps from value to another. Temperature is an analog quantity because temperatures do not jump from one degree to the next as there are many values in between. Digital quantities jump from value to the next. Computers are nearly always digital devices and can only operate with digital values. If analog values such as temperature readings need to be input into a computer, they need firstly to be converted to digital values using an analogue to digital converter.
