Meters Flashcards
What is an analog Meter
Pointer and scale indicates value
Common type of meter movement
D’arsonal movement
Often referred to as a moving-coil meter
What does a rectifier do
Changes AC voltage to DC voltage
What is a voltmeter
Designed to be connected directly across the source of power
Voltmeter- Calculating the resistor value
Operating characteristics of the meter must be known
Full Scale values of the meter
- Meter requires a current of 50 mA and a voltage of 1 V to deflect the pointer full scale
What is a Multi range Voltmeter
Designed to use one meter movement to measure several ranges of voltage
Calculating the resistor values
- values of four resistors shown can be determined using ohms law
Parallax effect
Viewing angle will effect reading
3 steps to reading a Voltmeter
- Determine what the meter indicates
- Determine the full scale value of the meter
- Read the meter
The Ammeter
What is it used for and how is it used
Used to measure current
Must be connected in series with the load to permit the load to limit current flow
What is a Shunt
A shunt is used to set the value of an ammeter
What is a MULTI range ammeter
Operate on more than one range
Done by connecting the meter movements to different shunts
Care must be taken so the shunt is never disconnected from the meter
What is the Ayrton Shunt
Connects shunt to meter movement
Why are shunts used with AC ammeters
To increase their range
Cannot be used to decrease their range
Most use a current transformer instead of
What is a clamp on ammeter
Meter is clamped around one conductor supplying power to the load
DC-AC clamp on ammeter
Most clamp on ammeters that have the ability to measure bother do not operate on current transformer principle
What is the Hall Effect (DC-AC ammeters)
Basic principal of operation
What is the ohmmeter
Used to measure resistance
Common VOM (volt-ohm-milliammeter) contains an ohmmeter
Basics types of analog ohmmeters: series and shunt
What does ohmmeter measure
Voltage drop accross a resistor
Never to be connected to a circuit if power is on
What is the low impedance voltage tester
Very large current draw compared to other types of voltmeters
Should never be used to test low power circuits
What is an oscilloscope
Is a voltmeter
Measure voltage during a period of time
Produces a two dimensional image
Voltage range selection - voltage and time base
4 oscilloscope considerations
Measuring frequency
Attenuated probes
Controls
Interpreting waveforms
What is the wattmeter
Used to measure power in a circuit
What are the two types of wattmeter
Dynamic and electronic
What is a recording meter
Record an electrical value over a long period of time
Produces a graph of metered values
Detect spike voltages, currents of short duration, or sudden drops in voltage, current, or power
What is a bridge circuit
Used to measure values of resistance, inductance, and capacitance accurately
