Module 3 -- Introduction to Circuit Protection, Control, and Measurement
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AI−1 to AI−3
AII−1 to AII−2
AIII−1 to AIII−10
a. Always connect a voltmeter in parallel.
b. Always start with the highest range.
c. Deenergize and discharge the circuit before connecting or disconnecting the voltmeter.
d. In a dc voltmeter, observe the proper polarity.
e. Never use a dc voltmeter to measure ac voltage.
f. Observe the general safety precautions of electric and electronic devices.
A42. Circuit continuity.
A43. The ohmmeter is connected in series with the resistance to be measured.
A44. An ohmmeter has several internal range resistors and a switch or a series of jacks to select the proper range.
A45. The middle of the scale.
A46. Series and shunt.
A47. Series ohmmeters have 0 on the right end of the scale and ∞ on the left end of the scale. Shunt ohmmeters are the opposite.
a. Deenergize and discharge the circuit before connecting an ohmmeter.
b. Do not apply power to a circuit while measuring resistance.
c. Switch ohmmeters to the OFF position, if provided, or to highest range and remove meter
leads from the meter when finished measuring resistance.
d. Adjust the ohmmeter after changing resistance range and before measuring reading
indicates the resistance.
A49. To measure high resistance.
A50. Connect one lead to the insulation and one lead to the conductor. Turn the handcrank until it starts to slip. Note the reading.
a. Use meggers for high-resistance measurement only.
b. Never touch the test leads when the handle is being cranked.
c. Deenergize and discharge the circuit completely before connecting a megger.
d. Disconnect the item being checked from other circuitry, if possible, before using a megger.
A53. A single measuring device capable of performing the functions of a dc voltmeter and ammeter, an
ac voltmeter and ammeter, and an ohmmeter.
A54. It is much more convenient to have one meter with several functions than several meters each with a single function.
A55. By changing the position of the function switch.
A56. The meter movement reacts to average ac voltage and current and the effective value is desired.
A57. To stop parallax error
A58. Make sure no image of the pointer is visible in the mirror when reading the meter.
a. Deenergize and discharge the circuit completely before connecting or disconnecting a multimeter.
b. Never apply power to the circuit while measuring resistance with a multimeter.
c. Connect the multimeter in series with the circuit for current measurements, and in parallel for voltage measurements.
d. Be certain the multimeter is switched to ac before attempting to measure ac circuits. e. Observe proper dc polarity when measuring dc.
f. When you are finished with a multimeter, switch it to the OFF position, if available. If there is no OFF position, switch the multimeter to the highest ac voltage position.
g. Always start with the highest voltage or current range.
h. Select a final range that allows a reading near the middle of the scale.
i. Adjust the "O ohms" reading after changing resistance ranges and before making a resistance measurement.
j. Be certain to read ac measurements on the ac scale of a multimeter.
k. Observe the general safety precautions for electrical and electronic devices.
A60. To measure current safely and easily (with no need to disconnect the wiring of the circuit).
A63. 5.945 megawatt-hours, or 5,945 kilowatt-hours, or 5,945, 000 watt-hours.
A64. Vibrating reed and moving disk.
a. A dc ammeter, 90 mA dc
b. A dc voltmeter, 200 V dc
c. An ac voltmeter, 4.6 V ac
d. An ohmmeter, 400 ohms
A66. (A) 410 mA dc; (B) 3.9 mA ac; (C) -22 V dc; (D) 600 V ac; (E) 1.4 V ac; (F) 1.9 NRKPV
A68. (A) Megger (megohmmeter), infinity; (B) Wattmeter, 9.5 kilowatts (9,500 watts). (C) Watt-hour meter, 2.693 megawatt-hours 2,693 kilowatt-hours) (2,693,000 watt-hours).
A70. (A) Vibrating-reed, 60Hz. (B) Moving-disk, 58 Hz.
NEETS Table of Contents
- Introduction to Matter, Energy,
and Direct Current
- Introduction to Alternating Current and Transformers
- Introduction to Circuit Protection,
Control, and Measurement
- Introduction to Electrical Conductors, Wiring
Techniques, and Schematic Reading
- Introduction to Generators and Motors
- Introduction to Electronic Emission, Tubes,
and Power Supplies
- Introduction to Solid-State Devices and
- Introduction to Amplifiers
- Introduction to Wave-Generation and Wave-Shaping
- Introduction to Wave Propagation, Transmission
Lines, and Antennas
- Microwave Principles
- Modulation Principles
- Introduction to Number Systems and Logic Circuits
- Introduction to Microelectronics
- Principles of Synchros, Servos, and Gyros
- Introduction to Test Equipment
- Radio-Frequency Communications Principles
- Radar Principles
- The Technician's Handbook, Master Glossary
- Test Methods and Practices
- Introduction to Digital Computers
- Magnetic Recording
- Introduction to Fiber Optics