Mod 7.3 (4) Flashcards
How do you reduce oscillation in a meter?
By electromagnetic dampening.
What is meant by the term full-scale current?
The amount of current that must flw through the meter coil to deflect the pointer over the ful scale.
What is the use of a thermistor in a D’arsonval meter?
The amount of resistance remains constant as the temperature changes.
How is the D’arsonval meter used as a current measuring device?
D’arsonval meter is used as a current measuing device by placing a resistor in parallel with the circuit.
What are the resistors in a voltmeter commonly known as?
Resistors in a voltmeter are called multipliers.
What use is a variable resistor in a series ohmmeter?
A variable resistor is used to ‘Zero’ the meter before each use.
What is the shunt-type ohmmeter used for?
The shunt-type ohmmeter used for measuring very low resistance.
What is the advantage of the ratiometer over the D’arsonval meter?
The ratiometer is independant of voltage fluctuations.
What is the difference between a bonding meter and a megger?
A bonding meter measures low resistance.
A megger measures high resistance.
On a megger, to which coil is the handcranked generator voltage applied?
The control coil is handcranked to apply voltage on a megger.
What is the range of a bonding meter scale?
Range of a Bonding Meter : 0-0.1ohm
What is the scale that a bonding meter is graduated in?
Scale that a bonding meter is graduated in:
0.002ohm divisions
What type of multimeter uses ‘zero’ adjust knob?
An analogue multimeter.
Define resolution of a digital multimeter:
Resolution refers to how small/fine a measurement meter can make.
Voltage measurements determine?
Voltage Drop
Volatge Imbalance
Source Voltage
An electrodynameter is used to measure?
An electrodynameter measures Power.
The formula for power factor is?
True power (watts)
÷
Apparent power (volts-amps)
The steps for measuring Current are?
Turn off power / cut or unsolder circuit to place the test leads
Select amps
Plug the black lead into the ‘com’ jack
Plug the red lead into 10amp jack
Connect probes across the break / turn power on
What type of meter is used to measure low resistances?
A shunt-type ohmmeter measues low resistances.
What type of meter measures high resistances?
A megaohmeter measures high resistances.
