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 circuit.
Series with the
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)