Unit1 measurement and tech(1b)
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This document discusses different ways of measuring time periods and intervals using various instruments. It defines time period and discusses the beginning and end of time periods in different contexts like a stopwatch or wave analysis. It also explains the difference between analog and digital systems and provides examples. Finally, it describes different instruments used to measure voltage, current, and signals over time like voltmeters, ammeters, multimeters, and cathode ray oscilloscopes. It explains how to use the controls on an oscilloscope to obtain a clear picture of the signal being measured.
Unit1 measurement and tech(1b)
- 1. Revision of concepts:Time Period:Definition:Space of seconds, minutes, hours, days, weeks, months or years with an established beginning date and ending date. It's a unit of measurement used to categorize a length of time. Also called timeframe.What is the beginning and end in physics?Different scenarios can have different types of beginnings and ends.E.g1: in a stopwatch, the instant you turn on the stopwatch: that time becomes the beginning time, and the instant you turn it off becomes your ending time.E.g2: In wave analysis, the time to complete one complete cycle is your time period, that maybe from node to node, crest to crest or trough to trough.Recall that T=seconds f=1/T hence, 1/s
- 2. Digital vs. Analog Analog:A system in which data is processed continuously, When you obtain a value of y for every corresponding value of x, then we are dealing with an analog system.Digital : A system in which data points are not continuous.Example: A string tied to a doorknob is a practical example of an 'analog' system. The string, when shaken, creates waves that travel down the length of the string until they hit the doorknob. A digital system would be more like flipping a light switch on and off. Speaking in general terms, there is no 'in between' values, unlike our doorknob and string example above.
- 3. measure time intervals using clocks, stopwatches and the calibrated time base of a cathode-ray oscilloscope (c.r.o.)use ammeters and voltmeters with appropriate scalesuse a cathode-ray oscilloscope (c.r.o.)(b) use both analogue scales and digital displays(c) use calibration curves
- 4. VoltmeterA voltmeter is an instrument used for measuring the electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to digital converter.
- 5. Analog and Digital VoltmetersAnalog Scale:Digital Scale:
- 6. Moving Coil AmmetersAmmeters, used to measure the current flowing into or out of the battery bank, are also available for a wide range of different applications from micro-Amps (e.g. in solar cell experimentation) to hundreds of Amps (e.g. in large wind turbines).
- 7. Analog and Digital Ammeters(in-line)AnalogDigital
- 10. An oscilloscope is easily the most useful instrument available for testing circuits because it allows you to see the signals at different points in the circuit. The best way of investigating an electronic system is to monitor signals at the input and output of each system block, checking that each block is operating as expected and is correctly linked to the next. With a little practice, you will be able to find and correct faults quickly and accurately.
- 11. The function of an oscilloscope is extremely simple: it draws a V/t graph, a graph of voltage against time, voltage on the vertical or Y-axis, and time on the horizontal or X-axis.
- 12. As you can see, the screen of this oscilloscope has 8 squares or divisions on the vertical axis, and 10 squares or divsions on the horizontal axis. Usually, these squares are 1 cm in each direction:
- 13. Adjust VOLTS/DIV and TIME/DIV until you obtain a clear picture of your signal:Set both VOLTS/DIV controls to 1 V/DIV and the TIME/DIV control to 0.2 s/DIV, its slowest setting:Lets have a look at a simulation: