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Question 1

What principles of the D’Arsonval, or moving coil meter make the meter work?

Answer 1

A coil of wire becomes an electromagnet when an electric current flows through it.
Like magnetic poles repel and unlike magnetic poles attract

Question 2

List the basic parts of a D’Arsonval meter

Answer 2

Moving coil wound on an aluminum frame
Moving coil is mounted with jewel bearings
Jeweled bearings allow meter to move freely between a permanent magnet
Pointer is attached to coil

Question 3

List the basic parts of a D’Arsonval meter

Answer 3

current being measured is conducted through the spiral springs
Mirror to assist in reading accurately
Zero-adjust screw is used to set the pointer to zero

Question 4

When current flows through the coil or the D’Arsonval meter what happens

Answer 4

magnetic field interacts with permanent mag
Produces clockwise torque on the coil
The torque, or turning force, is directly related to the amount of current flowing in the coil

Question 5

What is the D’Arsonval meter coil can handle without wrecking

Answer 5

50 mA

Question 6

Define deadbeat as it pertains to D’Arsonval meters

Answer 6

when the pointer move across the scale smoothly and reaching it steady position without oscillation due to effective damping

Question 7

What are the two types of damping used on D’Arsonval

Answer 7

Eddy-current damping

Air damping

Question 8

Greatest accuracy on a meter

Answer 8

select the range so that the needle will be a near as possible to FSD

Question 9

What are the three names for a meter

Answer 9

D’Arsonval
Moving coil
Galvanometer

Question 10

Accuracy of a meter is

Answer 10

ohms per volt or 1/amps or the current though the coil

Question 11

To get an accurate reading on a voltmeter

Answer 11

the total resistance of the meter should be about 10 times that of the load under test

Question 12

Why must an amp meter have short switch on it amperage range selection switch

Answer 12

if it did not have the make-before-break switch the coil would get full amperage for a split second. Can only handle up to 50 mA

Question 13

Amp meter sensitivity is defined as

Answer 13

the amount of current necessary to cause FSD. The lower the current to cause FSD the better sensitivity the meter has.

Question 14

Define meter loading

Answer 14

when the meter being used changes the values of the current or voltage being measured due to adding or removing resistance.

Question 15

External shunts are used

Answer 15

to measure large DC currents

Question 16

What two materials are shunts made of?

Answer 16

Copper and manganin

Question 17

What temperature coefficient does manganin have?

Answer 17

negative

Question 18

what resistance would a shunt have? high or low

Answer 18

low. must be able to conduct large amounts of current

Question 19

List the fundamental parts of an AC clamp meter

Answer 19

Iron Core, clamp, secondary coil

Question 20

AC clamp ammeter operates on the principle of an

Answer 20

transformer

Question 21

If the current in the conduct is too small for your AC clamp ammeter what can be done?

Answer 21

Loop the wire around the clamp adding amperage for each turn.

Question 22

What is the movable coil in a watt meter called?

Answer 22

voltage or potential coil

Question 23

What two types of coils are in a watt meter

Answer 23

current carrying coil

voltage coil or potential coil

Question 24

what must be done when hooking up a watt meter to insure that the pointer defects the correct way

Answer 24

make sure that the terminals are connected to the one marked with an asterix or plus sign

Question 25

what keeps the pointer at zero when the meter is not registering any power

Answer 25

a spiral spring.

Question 26

List basic functions of Solenoid-and-Plunger voltage tester

Answer 26

when not in use the spring holds plastic disk t 0V
Higher the voltage the further the disk goes from 0V
On DC the tester doesn’t vibrate
On AC voltage the tester vibrate
Only use for 15-20 seconds

Question 27

A megger is used to

Answer 27

test the megaohm resistance of wire insulation

Typical meggar output voltage would be 100 to 1000V

Question 28

What should be done before and after meggering a conductor?

Answer 28

Short it to ground

Make sure that the conductor to be tested is not hooked to any electronic curcuits

Question 29

What does DMM stand for?

Answer 29

Digital Multi-Meter

Question 30

The impedance value of most digital voltmeters is

Answer 30

10 Megaohms

Question 31

List three causes of insulation deterioration

Answer 31

Oil
Moisture
Excessive heat
Mechanical damage

Question 32

what is the minimum value that is expected when meggering a motor conducto

Answer 32

1 Megaohm

Question 33

DMM have a

Answer 33

3.5 digit display

Question 34

For DMM accuracy

Answer 34

+ and - (%stated accuracy X reading) +

change in the number of least significant digit