Executive Summary 4
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- 3.10.5 Multi-meter
- 3.10.6 Oscilloscope
- 3.10.7 Analog Oscilloscopes
- 3.10.8 Digital Oscilloscopes
3.10.4 Vacuum Tube VoltmeterVacuum Tube Voltmeters were popular before digital multimeters were created. This voltmeter used an electromechanical meter to measure the output rather a display. Rather than using the current form the circuit, an amplifier supplies the current needed to move the meter to display the voltage. Since an electronic amplifier between input and meter is used, a more rugged moving coil instrument can be used since sensitivity is no longer a requirement. The figure below is a picture of a vacuum tube voltmeter. 
(http://plymouthcolony.net/starcity/radios/pages/hp-vtvm.html) (Reprinted with permission from plymouthcolony.net) Modern version of vacuum tube voltmeters use field effect transistors in their solid state amplifiers rather than the actual vacuum tube that the voltmeter was originally named after. The modern version of this are referred to as FET voltmeters. Just like the digital voltmeter, the vacuum tube voltmeter has consistent impedance no matter the size of range of the measurement. The amplified meters generally use an input impedance of 1, 10, or 20 megaohms. With the sensitive rugged coil and the solid-state amplification, vacuum tube voltmeters are good for measuring lower voltages. 3.10.5 Multi-meterA multi-meter is a combination of different electrical meters together into one device. It is also described as a volt/ohm meter, VOM, and a multitester. Basic multi-meter models can usually measure voltage, current and resistance. Advanced models can measure more variable such as temperature, inductance, capacitance, duty cycle and frequency. The most models have a display, terminals, probes and a dial to select the different measurements and their ranges. The figure below is a picture of a multi-meter. 
(http://rcboatparts.com/supplies.html) (Reprinted with permission from rcboatsparts.com)
An oscilloscope is a device that not only measures voltages but has the ability to present them in a wave form. The output can display multiple voltages in a graph plotted as a function of time. The oscilloscope allows users to view the amplitude and frequency of a voltage. Users can see the distortion of the measured voltage as well as the time between pulses. The figure below is a picture of a oscilloscope. 
(http://www.best-microcontroller-projects.com/how-to-use-an-oscilloscope.html) (Reprinted with permission from best-microntroller-projects.com) 3.10.7 Analog OscilloscopesAnalog oscilloscopes use an attenuator to reduce the voltage and an amplifier to increase it. The voltage comes through the connected probes which sets the machine in parallel just as the voltmeter would. The voltage signal flows to a cathode ray tube. This displays a moving glowing dot that moves up for a positive voltage and down for a negative voltage. The oscilloscope uses a trigger system called a horizontal sweep. This system allows the dot to move across the screen rather than only in a vertical direction. This gives the motions of the wave in a left to right display. Several rapid sweeps, up to 500,000 times a second, allows the dot to be a seen as a solid line. The combination of the vertical movement and the horizontal sweep creates the graph of the voltage. The trigger system stabilizes the signal so that the sweeps begins at the same point creating a clear image. 
(Reprinted with permission from hobbyprojects.com) The figure above displays two screens: one of an untriggered display and one of a triggered display. The untriggered display shows the graph with multiple lines showing the repeating signal as if there were more than one signal. The trigger display stabilizes the repeating signal to presents the signal as a clear wave.
(Reprinted with permission from hobbyprojects.com)
Digital oscilloscopes work similar to their analog counterparts except that it includes extra data processing systems that collect data from the waveform to display. The digital oscilloscope connects in parallel to the circuit, using probes, and a vertical system works to display the amplitude for the signal. The acquisition system uses an analog to digital converter to takes sample points. The points are discrete points in time and are converted to digital values. The horizontal system regulates how often the acquisition system takes sample points using its sample clock. The number of times the sample point is taken per second is referred to as the sample rate. The analog to digital converter gathers the sample points and stores them as waveform points. These points can be made up or several sample points. After the waveform points are stored and saved, they are collected to create a waveform record. The start and stop points of the record are determined the trigger system. The number of waveform points saved to form the waveform record is referred to as record length. The record is stored and then the accumulation of points is then displayed for the user. The additional data processing systems can be perform and displayed also. These displays are can include a pre-trigger that enables you to see points before trigger point, peak detection, same time sampling and the average across consecutive samples. 
http://www.hobbyprojects.com/oscilloscope_tutorial/oscilloscope_working.html (Reprinted with permission from hobbyprojects.com) The figure above displays the way a digital oscillator operates. First the probe is connected to the circuit where the unknown voltage is. The signal will go through the vertical system, which consists of an attenuator and vertical amplifier just as it did with the analog oscillator. The signal then goes to the trigger system and the horizontal system. At this time the clock rate is set. The signal then goes through acquisition system where it is converted to a digital signal, stored in the memory and processed for other features. The acquisition system also uses the clock rate that was set. The signal is then ready for display. Directory: seniordesign seniordesign -> Hvac control and Feedback System 0 Group 2 Steve Jones Mathew Arcuri Elroy Ashtian, Jr seniordesign -> Group 5 Spr-Sum 2011 seniordesign -> Senior Design II paper seniordesign -> Remote Touchscreen-Controlled Defense Turret Senior Design Documentation Courtney Mann, Brad Clymer, Szu-yu Huang Group 11 seniordesign -> Flight Performance Data Logging System seniordesign -> Amphibious vehicle seniordesign -> T-100 Watch Dog (Autonomous Security Vehicle) seniordesign -> Ehvac: Wireless Modular Multi-Zone hvac controller Group b javier Arias Ryan Kastovich Genaro Moore Michael Trampler seniordesign -> Table of Contents Executive Summary 2 Download 0.5 Mb. Share with your friends:
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