C4 LT1 Flashcards
How do digital multimeters measure the waveforms under test?
True RMS or average responding methods
What are digital voltmeters commonly used for?
Voltage measurements
What is a DC voltage source?
Unidirectional current flow
What is the purpose of a diode?
Allows current to flow in one direction only
In what configuration is the meter placed with the device being measured?
In parallel
How is DC voltage usually supplied?
From a battery or power supply
What voltage is approximately for most silicon diodes?
0.7volts
What does a digital multimeter with autoranging feature do?
Automatically select the best accuracy and resolution range
What creates AC voltage?
An Alternator at a hydroelectric plant
What is a rectifier used for?
Convert AC to DC
What does the continuity function of a DMM do ?
Verifys circuit completion
How can the autorange feature on a DMM be changed to manual range?
Using the range button
What is the AC voltage function used for?
Measuring changing voltage
How can DC voltage be produced?
Electromagnetism, chemicals, heat, solar panels
How can the current be measured with a standard DMM?
Interrupt circuit, connect in series
What does the function control switch on a digital multimeter do?
Selects the electrical quantity to be measured
What can a DMM set for the DC voltage function be used to test?
Battery banks, DC motors, DC generators
What type of current can clamp-on ammeters measure?
Alternating current
What is the difference between true RMS and average responding meters?
Integration circuit vs. simple circuit
What is the typical input impedance of most digital meters?
10 megohms
What does a digital ammeter measure?
Current in an electrical circuit
What is the relationship between induced voltage and the strength of the magnetic field?
Proportional
How can you determine if a DMM is a true RMS meter?
Check the manufacturer’s specifications
Why does a voltmeter with low resistance compared to the circuit give a false reading?
Changes the circuit by lowering resistance
What causes current to flow through a circuit?
Power source connected to a device
What can a clamp-on meter measure?
AC and DC voltages, resistance
What is the term for the effect a meter has on the circuit by increasing current flow?
Meter loading
What is current?
Flow of electrons when voltage is applied
What are the different types of alternators?
Steam-powered and wind-powered
What is current measured in?
Amperes or amps
What does AC voltage do?
Changes in magnitude and polarity
What can most DMMs measure in terms of current?
Micro-amp range to 10 amps
Are clamp-on current probe accessories available for both AC and DC currents?
Yes
What is the voltage produced by a DMM in diode test mode?
2.5 volts
What can the continuity function be used for in troubleshooting?
Test components like fuses and switches
How does a DMM indicate continuity?
Audible signal or tone
What is the maximum current measurement for most DMMs?
10 amperes
What will the display indicate on a DMM when the measurement value exceeds the selected range?
OL (overload)
What does a true RMS meter use to compute the RMS value of the waveform under test?
Integrated circuit
What type of circuits require a true RMS DMM for accurate measurement?
Lighting circuits with electronic ballasts, circuits with variable-speed drives, and computers
What does input impedance limit when taking measurements with a meter?
Current drawn by the meter
What effect can occur if a voltmeter has a resistance that is too low in comparison to the circuit?
False reading due to meter loading
Why are current measurements taken?
To ensure circuit is not overloaded
How do clamp-on meters measure current?
Current transformer
Where is the AC voltage function commonly used?
Testing and troubleshooting AC circuits
What are the types of digital ammeters?
Panel mount, bench, clamp types, DMMs
Where is the core material of the current transformer located?
Jaw of the meter
What are clamp-on current probe accessories used for?
Measure higher current values and safely take current readings without opening a circuit.
What induces voltage in the current transformer?
Changing magnetic field
How do clamp-on ammeters measure current?
Hall effect generator principle
