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Laboratory 10: AC Measurements

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Laboratory #10:

AC Measurements

Objectives:

This exercise introduces the operation and use of the AC wattmeter, as well as single-phase se-

ries circuits containing resistance, inductance, and capacitance. It uses the oscilloscope to meas-

ure the phase shift of current through reactive circuits.

Pre-Lab:

1. Study Appendix B regarding Wattmeter, especially “Three-Phase Power Measurements”.

2. Study Appendix D information regarding using the oscilloscope to measure phase shift.

3. Study textbook regarding calculation of impedance and power factor for reactive loads.

4. Review phasor diagrams for voltage and current.

Safety Precautions:

1. Care must be used in working with the autotransformer (Variac

) power supply used in this

lab. Avoid touching conducting portions of a circuit when power is on. In particular, never

touch two separate portions of such a circuit with both hands.

2. The ± polarity terminals of the wattmeter’s voltage and current coils are usually connected

together.

3. A voltmeter or wattmeter’s voltage coil must be connected in parallel with the load or

source being measured.

4. An ammeter or wattmeter’s current coil must be connected in series with the load.

Equipment Needed:

 AC voltmeters

 AC ammeter

 Wattmeter

 Power decade resistor box

 120 mH inductor

 40 µF capacitor

 Autotransformer power supply

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BK Precision 4011A Betriebsanleitung Seite 38