Electrical Meters and Measurements
A digital multimeter is a single instrument that is capable of measuring voltage, current and resistance. A digital multimeter is an indispensable general-purpose tool for troubleshooting electrical problems. There are other dedicated test instruments, which in various ways, go beyond the capabilities of the multimeter. This module describes the typical features and usage of digital multimeters, as well as those of voltage detectors, clamp ammeters, megohmeters, digital thermometers and oscilloscopes.
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Learning Objectives
• List precautions to be taken when making electrical measurements • Describe a digital multimeter • List what can be measured with a multimeter • Describe how voltage, current and resistance are measured • Describe the advantages of a voltage detector • Describe a clamp ammeter • Describe what is unique about a megohmmeter • Describe how an oscilloscope can be used
Specs
| Course Level | Intermediate |
| Languages | English |
| Compatibility | Audio, Video |
| Based on: | Industry Standards and Best Practices |
Key Questions
What measurements can be made with a digital multimeter?
A digital multimeter is a single instrument that is capable of measuring voltage, current, and resistance. Some models may include the ability to perform capacitance measurement, diode or transistor testing, and temperature measurement.
What are the basic external features of a digital multimeter?
A digital multimeter consists of three major external features, a display, a function selection knob, and test lead ports.
What is the biggest advantage of a clamp ammeter?
A clamp ammeter can measure the electrical current in line without having to stop the current and “break into” the line. The current is measured by simply enclosing a wire within movable clamp arms of the instrument.
What is a megohmmeter?
A megohmmeter is an instrument designed to measure very high electrical resistance materials such as the resistance in insulation surrounding a wire.
What are the benefits of an oscilloscope?
An oscilloscope displays a graph on a screen showing how a voltage signal changes with time. Oscilloscopes can display a signal change that occurs in as little as a millionth of a second.
Sample Video Transcript
A digital multimeter can also be used to measure current flow in amperes, or amps. In order to use a digital multimeter as an ammeter, the main selection dial needs to be set to the correct current measurement range, and one of the leads needs to be moved to a current measuring socket. In order to measure current, it must flow through the meter. This requires disconnecting the power source, connecting the meter into the circuit, and then reconnecting the power. This is more difficult and dangerous than simply touching a probe to a contact to measure voltage.
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