Download lab 5 measuring voltages

LAB 5 MEASURING VOLTAGES
May 2, 2017
Lab 5 Set-up and Figure 1
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LAB 5 MEASURING VOLTAGES
May 2, 2017
OVERVIEW:
Voltage measures potential difference, which causes electrons to move through a completed
circuit. Current is the rate of flow of these electrons. The power source in a circuit provides the
voltage. Polarity describes the orientation of the positive (+) and negative (-) terminals of a
power source or measuring device used in a circuit.
Electrons move through a circuit in two ways. Direct Current (DC) moves in only one
direction, and is the result of a constant polarity power source such as a battery. Alternating
current (AC) moves in two opposite directions, in a regularly alternating pattern. AC is the result
of a power source with changing polarity, such as an AC generator.
Batteries are voltage sources that derive their energy from a chemical reaction. Batteries can be
connected together to increase or decrease the total voltage of the power source. To increase
voltage, the positive terminal (cathode) of one battery is connected to the negative terminal
(anode) of the next battery. (Fig. A)
If you reverse the polarity of one of the batteries, that battery opposes the others, and lowers the
total voltage. (Fig. B)
Figure A
.
Figure B
Batteries may also be connected in parallel. They must be equal in voltage. The voltage is not
increased, but each battery supplies only part of the current, so they will last longer.
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LAB 5 MEASURING VOLTAGES
May 2, 2017
OBJECTIVES:
A) Measure AC and DC voltage sources using an analog meter.
B) Measure voltage sources using a digital multi-meter (DMM)
C) Connect batteries together to increase or decrease voltage.
EQUIPMENT REQUIRED:
Snap leads for 9-Volt Battery
Analog Multi-meter with probes
Digital Multi-meter with probes
Circuit Panel Easel
Universal Lead Set
9-Volt battery
Three 6-Volt batteries
PROCEDURE: All voltage measurements will be taken with both the analog and the digital
multi-meter, using the probe connectors.
A) MEASURING AC VOLTAGE SOURCES
1. Set the analog multi-meter function switch to AC Volts. Set the range switch to 250 V or 300
V. Connect the black probe to the "common" (negative) connection, and the red probe to the
positive (+) connection.
WARNING: Do not touch the probe tips together when
measuring the wall outlet voltage.
Use the analog meter to measure the voltage of the wall outlet
as shown in Figure 4. Record the reading in Data Table 1.
2. Set the digital multi-meter (DMM) function switch to AC.
Set the range to 200 V. Connect the black probe to the "com"
connection (common or ground) and the red probe to the
"V.0" connection. Turn the meter to "on", and measure the
wall outlet voltage. Record the reading, and turn the meter to
"off". Always turn the meter off when it is not in use.
B) MEASURING DC VOLTAGE SOURCES
1. Set the function switch of the analog meter to "+DC", and set the range
switch to 10 or 12 V. Measure the voltage of a single 9 V battery as
illustrated in Figure 5. Record the reading in Table
2. Repeat for a single 6 V battery.
3. Set the function switch of the DMM meter to DC and the range control
to 20 V. With the DMM, measure the voltage of both the 9 V and the 6 V
batteries. Record the voltage in Data Table 1.
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LAB 5 MEASURING VOLTAGES
May 2, 2017
C) MEASURING THE VOLTAGE OF BATTERY
COMBINATIONS
1. Connect together three 6 V batteries as shown in Figure
6. These three batteries are connected in series. Set the
range control of the analog meter to 25 or 30 V, and
measure the voltage of the three batteries as indicated.
Record the voltage as Battery Combination #1 in Data
Table 2.
2. Use the DMM, still on the 20 V-setting, to measure the
.same battery combination.
3. Reverse the polarity of battery 3, as shown in Figure 7.
Measure the voltage, and record the results as combination
#2 in Data Table 2.
4. Connect the snap leads to the 9 V battery. Remove
battery #3 from the circuit, and replace it with the 9 V
battery. Use the circuit panel as shown in Figure 8. Be sure
that the polarity of each battery is the same as in the figure.
Measure the voltage and record the results as combination
3 in Data Table 2.
5. Reverse the polarity of the 9 V battery. See Figure 9.
Measure the voltage and record the results as combination
#4.
6. Remove the leads from the batteries and disassemble the
equipment. Be sure to turn the DMM to "off" before
storing.
ANALYSIS: Discuss the questions on the back of the lab
form with your partners, and fill in the answers that you agree
upon. If you cannot agree on a specific question, ask for help
from the instructor.
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LAB 5 MEASURING VOLTAGES
Supervisor: ________________
OBJECTIVES:
May 2, 2017
Recorder: ______________ Tech: ________________
Date__________
SKETCH OF LAB SET-UP:
TABLE 1
Analog Multimeter
Digital Multimeter
Source
Voltage
Reading
VA
Switch Settings
Function
Switch
Range
Switch
(volts)
Voltage
Reading
VB
Switch Settings
Function
Switch
Range
Switch
(volts)
Wall
Outlet
9-V
Battery
6-V
Battery
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LAB 5 MEASURING VOLTAGES
May 2, 2017
DATA TABLE 2
Battery
Comb.
Analog Multimeter
Voltage
Reading
VA
Switch Settings
Function
Switch
Digital Multimeter
Voltage
Reading
VB
Range
Switch
(volts)
Switch Settings
Function
Switch
Range
Switch
(volts)
1
2
3
4
LAB #5
ANALYSIS:
1. A voltage with constant polarity (positive or negative) is called
______________________________
2. A voltage that changes polarity in a regular fashion is called
______________________________
3. Explain what range setting should be chosen to avoid damaging the voltmeter when measuring
an unknown voltage:
____________________________________________________________
4. Show a schematic diagram indicating 1.5 V batteries in series that will provide 4.5 volts:
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LAB 5 MEASURING VOLTAGES
May 2, 2017
5. Show schematic diagrams of two different combinations of 1.5 V, 6 V, and/or 9 V batteries
in series which will produce a total of 18 volts. (Don't use reverse polarity for either
combination.)
6. Show a schematic diagram with three 1.5 volt batteries in parallel.
A) What is the total voltage?___________
B) What advantage is obtained from connecting batteries in parallel?
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