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What meters operate from their own power sources?
Self-excited.
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What physical component of a galvanometer provides the restoring force for the coil?
Phosphor bronze ribbons.
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In a galvanometer, what two methods are used to indicate the amount of coil rotation?
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?
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?
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?
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?
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?
In parallel.
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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?
Ohms per volt.
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What instrument is used for measuring the insulation resistance of cables?
Megohmmeter (megger).
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What added features enable a dc milliammeter to function as an ohmmeter?
- A source of dc potential.
- 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?
Zero.
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The R x 100 resistance selection on an ohmmeter has what amount of resistance compared to the R x 10 selection?
1/10.
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What is the purpose of the guard ring in a megohmmeter?
Shunts leakage current, which prevents false readings.
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Most meggers you will use are rated at what voltage?
500.
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The development of excessive test voltages is avoided by the use of meggers equipped with what device?
Friction clutches.
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What components in an electrodynamometer-type meter movement produce the magnetic field?
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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