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30 Cards in this Set
- Front
- Back
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What meters operate from thier own power sources?
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Self-excited
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What physical component of a galvanometer provides the restoring force for the coil?
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Phosphor bronze ribbons
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In a galvanometer, what two methods are used to indicate the amount of coil rotation?
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The pointer arrangement and the light and mirror arrangement
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What is the primary disadvantage of the pointer arrangement for indicating coil rotation?
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Coil balance
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What component of the D’Arsonval meter movement completes the circuit for current flow to the
coil? |
Hairspring
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What component supplies restoring force to the coil of the D’Arsonval meter movement?
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Hairspring
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What advantage is gained by using pole pieces with curved faces in the D’Arsonval meter
movement? |
Makes it possible to have a more linear scale than if the poles were flat.
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What structurally large, low-resistance conductor is connected in parallel with the meter
movement to prevent damage? |
Shunt
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What type of temperature coefficient material does not produce increased heat in response to
increased current flow? |
Zero-temperature coefficient
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A good choice of shunt resistance will place the indicating pointer near what part of the meter
scale with a normal load? |
Midscale
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In what manner are current-measuring instruments connected to a circuit?
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In series
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An ammeter should always be connected so that current will flow into what terminal and out of
what terminal? |
Negative, positive
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(True or False) The larger the current required to produce full-scale deflection of the meter coil,
the better the sensitivity of the meter. |
False
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What condition exists when the insertion of a meter into a circuit changes the operation of the
circuit? |
Meter-loading
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What modification is made to the D’Arsonval meter movement to enable the meter to measure
voltage? |
A multimeter (high resistance) is placed in series with the coil of the meter
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What factors determine the value of the multiplier resistor?
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The current required for full-scale deflection, and the range of the voltage to be measured.
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In what manner are voltage-measuring instruments connected to the circuit to be measured?
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In paralell
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When making voltage measurements in a high-resistance circuit, you should always use a
voltmeter with what relative value of resistance? |
High
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What term is used to express the sensitivity of a voltmeter?
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Ohms per volt.
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What instrument is used for measuring the insulation resistance of cables?
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Megohmmeter (MEGGER)
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What added features enable a dc milliammeter to function as an ohmmeter?
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1) A source of dc potential. 2) One or more resistors (one of which is variable)
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A full-scale deflection on an ohmmeter scale indicates what resistance between the leads?
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Zero
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The R ´ 100 resistance selection on an ohmmeter has what amount of resistance compared to the
R ´ 10 selection? |
1/10
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What is the purpose of the guard ring in a megohmmeter?
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Shunts leakage current, which prevents false readings.
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Most meggers you will use are rated at what voltage?
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500
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The development of excessive test voltages is avoided by the use of meggers equipped with what
device? |
Friction cutches
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What components in an electrodynamometer-type meter movement produce the magnetic field?
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Fixed coils
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What is the limiting factor as to the amount of current an electrodynamometer meter movement
can handle? |
Size of spiral conducting
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What is the primary advantage of the electrodynamometer-type meter over the D’Arsonval-type
meter? |
The electrodynamometer-type meter can be used to measure both ac and dc currents
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