Electrical Measuring Equipment Flashcards
What do all electrical meters have in common?
They all have an internal standard to which measured values are compared.
How did digital meters get their name?
Comes from the fact that like a computer, all data is processed as discreet 1’s and 0’s
Digital meters all need…….
a signal processor
an analog to digital converter (ADC)
and a readout control
All integrating ADC’s use capacitors, they count the time it takes to fill and discharge a cap. to a reference voltage.
True
What is resolution in regards to digital meters?
deals with how finely the meter can distinguish between two values.
Accuracy in meters in expressed in ……….
a percentage.
What is the most common analog meter?
The D’Arsonval movement meter
Every digital meter requires an?
Analog to digital converter
The advantage of LCD over LED for meters is ……..
lower power consumption
Sensitivity of an analog meter is expressed in ……….
ohms per volt
What safety feature do meters have to protect the movement meter during switching between ranges?
Make then break switch
What will an accurate wattmeter always show you?
The true power consumed.
The jaws of a clamp on ammeter act like the secondary of a transformer with the being the primary.
conductor
An AC voltmeter has at least one in it.
Diode
Hands free voltmeter leads should be used when measuring circuits.
Moderate to high voltage
What is the purpose of rectifiers?
Convert AC to DC
What is at the end of an ohmeters scale is maximum resistance or……….
infinity.
The current flowing through an ohmmeter is very small values.
true
A shunt ohmmeter allows for measurements of much smaller resistances.
true
Do shorted capacitors exhibit any resistance?
No they are shorted
Graphical multimeters ac are capable of displaying…….
Spikes
Surges
sags
high speed transients
What can be viewed in TREND mode?
Monitor line voltages for sags and surges battery activity for charging and discharging cycles AC frequency changes intermittent breaks in continuity
What is the chief cause for catastrophic meter failure??
Unexpected overvoltage
Describe the CAT 1-4 in regards to electrical safety and equipment
CAT 1-very low voltage electronics
CAT 2- protected electronic equip/low voltage 120VAC
CAT 3-big appliances/machinery, MCC, Switchgear 240-480 VAC
CAT 4- Transformer yard, Transmission lines, Generating facility
What is needed to measure current greater than 10A with a multimeter?
A current probe of current transformer
Inscribed on oscilloscopes is a grid like pattern called a graticule.
Good units have the graticule inscribed on the inside.
Oscilliscopes have 2 kinds of sweeps (motion of the light) name them.
Free running ( charge up, discharge down) triggered sweep (predermined amount blanked off for accurate measure)
What is a dual trace oscilloscope?
It shows two waveforms at once, one above the other and can be produced three different ways.
Most oscilloscopes have the ability of interpolation or “fill in” between sample points
T
Slope ( which side of the x axis it will flow) and trigger controls (signal amplitude determines display) control when the display will register.
T
Circuit loading when measuring with an oscilloscope can be prevented by using a…….
attenuating probe
The reference signal jack , used when compensating the probe, delivers a……….
square wave form
What causes strong harmonics in the original voltage sign wave in an AC power line?
non linear building loads
