Electronics for Electricians 7E Unit 03.pptx

ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Unit 3 Measuring Instruments Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Objectives • After studying this unit the student should be able to: – Discuss the operation of a digita...

ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Unit 3 Measuring Instruments Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Objectives • After studying this unit the student should be able to: – Discuss the operation of a digital multimeter – Measure voltages with a digital multimeter – Measure resistance with a digital multimeter – Determine the amount of current flow in a circuit – Discuss the operation of an oscilloscope Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Objectives (cont’d.) – Discuss various oscilloscope controls – Connect an oscilloscope in a circuit – Interpret wave forms produced on the display of an oscilloscope Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Digital Multimeters • Digital multimeters – Employ a display to indicate the value – Exhibit the same amount of input resistance regardless of the range setting – Autoranging Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Digital Multimeters (cont’d.) Figure 3-9 Digital ohmmeters operate by measuring the voltage drop across a resistor when a known amount of current flows through it. Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Figure 3-10 The meter is connected in series with a load. Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Digital Multimeters (cont’d.) • Semiconductor test – Special range used to test semiconductor devices – Meter must provide enough output voltage to overcome the forward voltage drop of the device Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition The Oscilloscope • Volt-ohm-milliammeter (VOM) – Best way to troubleshoot circuits – However, many electronic control systems produce voltage pulses that are meaningless to a VOM • Oscilloscope – Used to learn what is actually happening in a circuit Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Oscilloscope Basics – Measures a voltage during a particular time period – Creates a two-dimensional image or picture – Divided into two main sections • Voltage section (Y-axis of the display) • Time base (X-axis of the display) Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Oscilloscope Basics (cont’d.) • Some common controls – Power – Beam finder – Probe adjust – Intensity and focus Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Oscilloscope Basics (cont’d.) • Some common controls – Vertical position – Ch 1—Both—Ch 2 – Add—Alt—Chop – AC—GND—DC Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Oscilloscope Basics (cont’d.) • Some common controls – Horizontal position – Auto—normal – Level – Slope – Int—Line—Ext Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Interpreting Waveforms • Display is the product of voltage and time • An image of the waveform can be downloaded into a computer and analyzed • Learning to interpret waveforms takes time and practice Copyright © 2017 Cengage Learning ELECTRONICS for ELECTRICIANS Stephen L. Herman Seventh Edition Figure 3-21 The grounded probe of the oscilloscope is connected to the ungrounded circuit conductor. Copyright © 2017 Cengage Learning