Meters Flashcards
There are five common meters used with electricity; what are these called and what do they measure?
- Voltmeter - voltage
- Ammeter - current
- Ohmeter - resistance
- Megohmeter - resistance of insulation
- Wattmeter - power
Four important factors must be considered when selecting a meter; what are these factors?
- What value is being measured?
- What is the expected magnitude of the value?
- Should the circuit be energized or not?
- Is polarity important?
What may cause error when taking an analog meter reading?
Parallax error.
You should read the needle from a position directly above it.
When connecting an analog DC voltmeter, to prevent damage what must always be considered?
Polarity. The needle could be “pinned” if improperly connected.
What is the voltage output for the majority of megohmeters?
500 - 1000 volts
When measuring the resistance of an energized load, what must one use to take a reading?
An Ohmeter.
- On a de energized load only.
- You must disconnect the circuit.
What is the danger present when using a dc voltmeter on an ac circuit?
It may indicate 0 volts when in fact there could be 120 volts.
How is an analog ohmeter “zeroed”?
Short out the leads and adjust a dial to 0.
How does a clamp on ammeter work?
It measures the strength of the magnetic field produced by current flowing in the conductor it is wrapped around.
When connecting a wattmeter, the current measuring portion must be connected in “_____” and the voltage measuring portion must be connected in “_____”.
- Series
- Parallel
Is it necessary to de energize a circuit when connecting a series ammeter?
Yes it is.
Which type of meter typically has a non linear scale?
A meter used to measure resistance.
When using a megohmeter to perform an insulation test, one lead is connected to the conductor, while the other is connected to…?
Ground or a reference point.
The red lead on a meter is typically the “_____” lead.
Positive or reference. (Determines polarity)
What does the range of a meter represent?
Full scale deflection at that setting.
