Transcript Basic Instruments and Measurements

Basic Instruments and
Measurements
Chapter 2
Basic Analog Meter
• D’Arsonval movement – stationary magnet,
moving coil galvanometer.
• Iron Vane Meter – two pieces of iron are placed
inside a hollow core solenoid.
• Current causes magnetic field to move a needle.
• Extreme caution and care when handling an
analog meter.
• Proper polarity must be maintained
Meter Scales
• Linear meter scale – marks are evenly
spaced.
• Note what range the dial of meter is set to
when reading the value of the scale.
Ammeter
• Measures electrical current in a circuit.
– Amperes
– Milliamperes
– Microamperes
• Shunt is used to direct excess current away
from meter.
• Always connected in Series with the
circuit.
Voltmeter
• Measures electrical voltage present in a
circuit:
– Volts
– Millivolts
• Connected in Parallel with the circuit
Ohmmeters
• Measures the resistance of a device or part of a
circuit:
–
–
–
–
Megaohms
Ohms
Milliohms
Microhms
• Zero the meter
• Battery inside the case used to measure resistance.
Other Meters
• Volt – Ohm – Milliammeter (VOM)
• Digital Multimeter (DMM)
• Computer Display meters
Electrical Diagrams
• Schematics
• Wiring Diagrams
• Symbols (see page 453 – 454)