Instrumentation and Control Systems ETP 2005 – Brian Vance This material is based upon work supported by the National Science Foundation under Grant No Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the view of the National Science Foundation (NSF).

Digital Using calculations by numerical methods or by discrete units In digital technology, the analog wave is sampled at some interval, and then turned into numbers that are stored in the digital device. On a CD, the sampling rate is 44,000 samples per second. So on a CD, there are 44,000 numbers stored per second of music. To hear the music, the numbers are turned into a voltage wave that approximates the original wave. com /question7.htm

Analogue  Of a circuit or device having an-output that is proportional to the input Analogue Data  Can be any value within a defined range. An analogue sound level can have any loudness between zero and the maximum recorded as well as any frequencies between the highest and lowest recorded.

Analogue Data Can be any value within a defined range. An analogue sound level can have any loudness between zero and the maximum recorded and any frequencies between the highest and lowest recorded.

Examples of Analogue  A traditional watch face is an analogue output  A vinyl record is an analogue storage device

The two big advantages of digital technology are:  The recording does not degrade over time. As long as the numbers can be read, you will always get exactly the same wave.  Groups of numbers can often be compressed by finding patterns in them. It is also easy to use special computers called digital signal processors (DSPs) to process and modify streams of numbers.

Binary  Relating to, being, or belonging to a system of numbers having 2 as its base (binary digits 0 &1)  Involving a choice or condition of two alternatives (yes or no, on or off)

Binary  Binary (meaning 'two') is the ones and zeros that computers use. The reason for this, is that there are only two states an electrical circuit can be in. Known as on and off or 1 and 0, 1 for on and 0 for off.  By grouping 1's and 0's together, a computer, or electrical circuit can create letters numbers and 'True' or 'False. Every bit of info in a computer has a binary code assigned to it and the computer knows these, for example, the letter 'A' converts to ' ' in binary.

Microprocessor  Integrated circuit semiconductor chip that performs the bulk of the processing and controls the parts of a system

Examples of Microprocessor-Based products:  Home appliances: VCR, Microwave, etc.  Cameras: still, video, digital  Automotive:, Comfort control, ABS, communication Engine control, Trip computer  Vending machines  Industrial equipment: Robots, Machine tools, Quality testing

Fuzzy Logic  A form of mathematical logic in which truth can assume a continuum of values between 0 and 1  Fuzzy logic is a superset of conventional (Boolean) logic that has been extended to handle the concept of partial truth -- truth values between "completely true" and "completely false". It was introduced by Dr. Lotfi Zadeh of UC/Berkeley in the 1960's as a means to model the uncertainty of natural language.

Examples of Fuzzy Logic:  Fuzzy logic is used directly in very few applications. The Sony PalmTop apparently uses a fuzzy logic decision tree algorithm to perform handwritten (well, computer lightpen) Kanji character recognition.

More Examples of Fuzzy Logic:  Regulating auto antilock braking systems  Camera auto focusing  Automating laundry machine operation  Controlling Video camcorders image positions

Neural Systems  Artificial intelligence used in systems to a variety of different things

Sensors  A device that responds to a physical stimulus (as heat, light, sound, pressure, magnetism, or particular motion) and transmits a resulting impulse (as for measure or operating a control)

Examples of Sensors:

Actuators  An actuator is a piece of equipment that produces movement when given a signal. Actuators are used in the computer control of an environment, industrial automation and in robotics There can be tree types: Electrical Hydraulic (work by liquid pressure) Pneumatic (work by air pressure)

Examples of Actuators:  A valve in the greenhouse may be closed to restrict the flow of hot water through radiators and pipes.  Another motor or actuator will lower blinds to reduce the amount of direct sunlight. resources.co.uk/Actuators.htm

Stepper Motor  A motor whose driveshaft rotates in small steps rather than continuously  Stepper motors are electromagnetic actuators that convert input pulses to output motion. They are different from ordinary current (DC) motors, in that, when energized by a voltage or current pulse train, the step motor moves in incremental amounts for each pulse it reads.

Examples of Stepper Motors:  Stepper motors are commonly used in computer peripheral equipment such as printers, tape drives, and disk drives. Additionally, they are used in machine tool controls, process control systems, robots and other industrial applications.

Synchro Motor  A system consisting of a generator and a motor so connected that the motor will assume the same relative position as the generator; the generator and the motor are synchronized  The synchro is a type of rotary electrical transformer that is used for measuring the angle of a rotating machine  The synchro was developed during World War II as part of a servomechanism that was used to synchronize the movement of a gun turret to a control dial.

Examples of Synchro Motors: Defying gravity, this window-climbing robot toy can easily scale smooth surfaces like windows, mirrors, and file cabinets. Using an ingenious system of four powerful suction cups, our Wild Climber Tree Frog’s precision release capability enables two feet to disengage and advance while the other two support its weight. The synchronized movement is a marvel to behold. For safety reasons, do not use on ceilings, or above head height. Requires two AA batteries. For age six through adult.

Open-Loop Control  In an open-loop control, the sequence of commands in the program is carried out irrespective of the consequences.

Examples of Open-Loop Control:  Switch a microwave on to defrost for 2 minutes. The turntable will turn and the food be microwaved for 2 minutes irrespective of whether it is thoroughly defrosted or not.  Program a toy robot to walk in a certain direction. It will follow all instructions even if there is an obstacle in the way.  Switch a sprinkler system on to water the garden at set times. Your garden will continue to be watered at these times even if it is pouring.

Closed-Loop Control  A closed-loop control system is one that involves feedback to ensure that set conditions are met.

Examples of Closed-Loop Control:  Any system that attempts to maintain a constant temperature involves feedback:  Central heating and air conditioning systems  Ovens  Tropical fish tank  Refrigerator  Freezers

Instrumentation  The use or application of instruments (as for observation, measurement, or control)

Examples of an Instrumentation:  Thermistors are thermally sensitive resistors and have, according to type, a negative (NTC), or positive (PTC) resistance/temperature coefficient.

Examples of Theristors: Engine Management:  Information displays  Climate control  Circuit protection

More Thermistors Found in Appliances:  Washing machine  Dishwasher  Microwave oven  Toaster

Standards Addressed  Standard 2  Benchmarks Y, DD, FF  Standard 3  Benchmarks H, J  Standard 17  Benchmarks M, O, P, Q