Chapter 3 signal-generator


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Chapter 3 signal-generator

  1. 1. MEASUREMENT 3.0 EE101 / CHAPTER 3 / 1 OSCILLOSCOPE AND SIGNAL GENERATOR 3.5 Understand signal generators 3.5.1 Define signal generator. 3.5.2 Classify types of signal generators. 3.5.3 Explain standard signal generators. 3.5.4 Explain function generator. 3.5.5 Draw and label the front panel of a signal generator. 3.5.6 Describe the function of the following items located on the panel of a signal generator: a. Frequency Selection group b. Sweep group c. Amplitude Modulation group d. DC Offset group e. Function or Waveform group f. Output group 3.5.7 Construct simple circuit with signal generator used as a signal source to the circuit. 3.5.1 Define signal generator A signal generator is a vital component in a test setup, and in electronic troubleshooting and development, whether on a service bench or in a research laboratory. Signal generators provide a variety of waveforms for testing electronic circuits, usually at low power. 3.5.2 Classify types of signal generators  Audio-frequency signal generator It has a selection of fixed waveforms, including sine, triangle, square and sawtooth. The best signal generators have waveforms of very high purity to look for harmonic distortion.  Radio signal generators Radio signal generators cover a higher frequency range than audio, to hundreds of megahertz or more. They're used to test radio broadcast equipment. Generating radio frequencies with precision is more difficult than audio, so these signal generators are more expensive.  Microwave signal generator. These signal generators produce frequencies into tens of gigahertz. They're used to test communications equipment and radar. As the frequencies are even higher than for radio, and since the equipment is more specialized, it's more expensive.
  2. 2. MEASUREMENT  EE101 / CHAPTER 3 / 2 Logic signal generators Engineers who build computer-related equipment need logic signal generators. These produce a variety of high-frequency pulses modulated by data. Since data is specific to an application, the signal generators relate to external data sources.  Arbitrary signal generator. A traditional signal generator produces a fixed set of waveforms, such as sine and sawtooth. An arbitrary signal generator lets you create and program a waveshape, which is then produced at the frequency you set. These generators are digital in nature, creating the wave shapes from a data table. 3.5.3 Explain standard signal generators The sine wave generator represents the largest single category of signal generator. This instrument covers a frequency range from a few Hertz to many Giga-Hertz. The sine wave generator in its simplest form is given in figure below; Set Level Set Frequency Attenuator RF Output Basic Sine Wave Generator The simple sine wave generator consists of two basic blocks, an oscillator and an attenuator. The performance of the generator depends on the success of these two main parts. The accuracy of the frequency, stability, and freedom from distortion depend on the design of the oscillator, while the amplitude depends on the design of the attenuator.
  3. 3. MEASUREMENT EE101 / CHAPTER 3 / 3 3.5.4 Explain function generator A function generator is a device which produces simple repetitive waveforms. Such devices contain an electronic oscillator, a circuit that is capable of creating a repetitive waveform. (Modern devices may use digital signal processing to synthesize waveforms, followed by a digital to analog converter, or DAC, to produce an analog output). The most common waveform is a sine wave, but sawtooth, step (pulse), square, and triangular waveform oscillators are commonly available as are arbitrary waveform generators (AWGs). If the oscillator operates above the audio frequency range (>20 kHz), the generator will often include some sort of modulation function such as amplitude modulation (AM), frequency modulation (FM), or phase modulation (PM) as well as a second oscillator that provides an audio frequency modulation waveform. Function generators are typically used in simple electronics repair and design; where they are used to stimulate a circuit under test. A device such as an oscilloscope is then used to measure the circuit's output. Function generators vary in the number of outputs they feature, frequency range, frequency accuracy and stability, and several other parameters. 3.5.5 Draw and label the front panel of a signal generator The front panel is divided into six major control groups: 1. Frequency Selection Group; 2. Sweep Group; 3. Amplitude Modulation Group; 4. DC Offset Group; 5. Function, or Waveform Group; and 6. Output Group.
  4. 4. MEASUREMENT EE101 / CHAPTER 3 / 4 3.5.6 Describe the function of the following items located on the panel of a signal generator: a. Frequency Selection group These controls are used to select the operating frequency of the function generator. This group consists of the frequency control knob and the eight frequency multiplier selection buttons. b. Sweep group The sweep group can frequency sweep any of its function outputs. It could be swept up or down in frequency using linear or log sweeps. Unlike function generators, there are no annoying discontinuities or band-switching artifacts when sweeping through certain frequencies. Two sweep marker frequencies can be specified. When the sweep crosses either of the marker frequencies, a TTL transition is generated at the rear-panel output to allow synchronization of external devices. c. Amplitude Modulation group It attenuates the sine wave in 3 decades, x1, x0.1 and x0.01. It provide 20dB of attenuation of the output waveform selected by function switch. d. DC Offset group To allow the DC level of the output waveform to be set as desire e. Function or Waveform group This group is used to select the shape of the generated waveform. The group is made up of the six wave-selector buttons. The six waveforms that the function generator can produce are the sine wave, the square wave, the triangle wave, two sawtooth waves, and the variable-width pulse wave. f. Output group These controls are used to adjust the amplitude of the generator's output signal.
  5. 5. MEASUREMENT EE101 / CHAPTER 3 / 5 3.5.7 Construct simple circuit with signal generator used as a signal source to the circuit Simple circuit with signal generator as a signal source