C-4 Flashcards
What is a DMM? What does it measure?
Digital Multimeter (combination of ammeter, voltmeter, ohmmeter) measures voltage, current, resistance, frequency, and temperature
A DMM Ammeter measures up to how much current?
10A
A digital Clamp-On ammeter allows you to take circuit current measurements without interrupting or opening circuit. True/False
True
Which DMM setting would be used to measure voltage output of a Alternator and Rectifier
Alternator : AC volt Rectifier : DC volt
Which meter function would be selected to provide quick and easy testing of whether a fuse is open or has a complete path through (continuity)
Continuity function of a DMM
Which measurement function of aDMM requires an internal battery to provide current flow through circuit?
resistance
Which feature of a DMM would be used to test rapidly changing signal?
bar graph
What CSA standard covers workplace electrical safety?
Z462-08
When connecting a DMM in line to measure AC amps, red test leads go into the _____ current jack
highest current jack
A DMM set for ohms is tested on an energized circuit, what happens?
damaging of meter
What is transient voltage? Why do they occur
Transient voltage is a temporary voltage spike in an electric circuit because of lightning strikes, unfiltered equipment, power being switched on and off
AC and DC voltmeters must be connected in parallel to circuit. True/False
True
AC and DC ammeters must be connected in series to prevent shorts. True/False
True
Black lead in the com(common) jack which is the ______ lead of the circuit.
negative
Red lead should be in V/resistance jack and connected to ______ lead
positive
The digital wattmeter’s current jack must be connected in series. True/False
true
The digital wattmeter’s voltage jack must be connected in parallel. True/False
true
What should always be done with a conductor before and after testing the conductor
grounding conductor
Minimum reading when meggering motor conductor
1mega ohm
What are meggers used for?
Used to check conductors installed in conduit or raceway for grounds, shorts, opens. testing insulation electrical equipment for resistance changes
What unique function does a clamp on ammeter have?
allows hold button, measures in rush current from motor startup
megger supplies voltages from ____ volts DC to ____ volts DC
250 to 5000
Digital insulation testers are also known as ______?
meggers
Cause of insulation deterioration?
mechanical damage, fault current, excessive heat, oil, moisture, voltage stresses
non-sinusoidal waveforms such as electronic ballasts require RMS or average responding meter.
True RMS
two methods of measuring waveform in DMM
True RMS, Average responding meter
The effect a meter has on the circuit
meter loading
most DMM’s have an input impedance of about?
10megaohms
A rectifier converts ____ to ____
AC to DC
Maintenance of digital meters include
Calibration, inspection, service, battery replacement, fuse replacement
Causes of false readings on a DMM on a de-energized circuit
Capacitive coupling
What are false readings called?
ghost, stray voltage
The resolution is the smallest measurement of the scale that can be shown on the display. True/False
True
The Autopolarity feature indicates that lead polarity is reversed for DC measurements. True/False
True
Autoranging automatically selects the proper measurement range. True/False
True
In manual range, what is shown on the display if the range is too low for measurement?
Overload (OL)
Meters have a window called display. True/False
True
LED or LCD to display digits. True/False
True
The display is uniquely energized by analog to digital electronic circuity. True/False
True
Meter test leads can be replaced with the cheapest leads? True/False
False
If a meter fuse is blown, it can be replaced with any fuse. True/False
False
If a battery symbol appears on the display, the battery needs to be replaced. True/False
True
How do you test the leads of a DMM?
change to resistance function and touch leads together, the display reads 0.5 ohms or less.
