Exp 1 Multimeter,Breadboard and Power Supply (2012)

7/22/2019 Exp 1 Multimeter,Breadboard and Power Supply (2012)

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Universiti Sains MalaysiaElectrical & Electronic Engineering DepartmentBasic Circuits Laboratory EEE125

Multimeters, Breadboard and Regulated DC Power SupplyOBJECTIVE

To become familiar with using a digital/analog multimeter, breadboard and regulated DCpower supply.

To become familiar how to configure basic measurement tools based on theircapabilities.

INTRODUCTION

Multimeter

A multimeter is an electrical instrument designed to measure voltage, current, resistance andoften other variables as well. Some of the recent multimeters are capable of testing diodes andtransistors as well. Multimeters are manufactured in both digital and analog form. A digitalmultimeter is preferred for precision work, but analog meters are also useful for gaining anintuitive understanding of instrument sensitivity and range. A digital multimeter (DMM) gives amore accurate digital readout over the less expensive analog models that have a needle thatmoves over a set of printed numbers on the dial. The digital multimeter is very close to being aperfect voltmeter, with a very high input resistance and a very low input current.

The multimeter is capable of measuring voltages, currents, resistance, waveform frequency (orperiod), and even short circuits (continuity). Given the wide range of measurements that arepossible with this device, it is easy to see why it has become such an indispensable tool in lab.

Due to the complexity of the internal circuitry which makes up the multimeter, however, we willfocus mainly on learning how to perform some common measurements which will be usefulthroughout the semester. Before jumping straight into the measurement procedures, let us take abrief look at the multimeter control panel as in Figure 1 and Figure 2.

A multimeter normally has:

1. Function/Range Switch - selects the function (voltmeter, ammeter, or ohmmeter) and therange for the measurement.

2. Input Terminals - to be connected in series (for current measurement) or in parallel(for voltage and resistance measurement) with the component of interest.

There may be an internal fuse or a cut out to prevent excessive currents in ammeter mode,which otherwise might damage the instrument.


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Figure 1: External view of an analog multimeter

Figure 2: External view of a digital multimeter


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DC Power Supply

Figure 3 shows a laboratory DC Power Supply that we will use for most of the experiments.

Figure 3: GW GPR3030 DC Power Supply

You should take note that there are three banana jacks for output of power supply. The output isusually used to support digital circuits and analogue applications. The output can be configured tobe positive (+ve) or negative (-ve) output depends on the selection of banana jacks. Voltage andcurrent meters indicate the desired output you need. Notice that the output only accepts bananaplug cables. Wires can be clamped into the terminals but this is usually more trouble that itsworth.

Breadboard/Protoboard

We will be making use of a breadboard for constructing our lab circuits. The layout of thebreadboard allows us to quickly construct and test circuits without the need for complicated wiringor soldering. Figure 4illustrates the internal wiring of the breadboard.

Figure 4: Internal connections of a breadboard


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Note:The dark center strip indicates that the five columns to the left are electrically isolated fromthe five columns two the right. That is, no physical connection exists between them.

As shown in Figure 4, there are 4 columns which are connected vertically. That is, a voltageapplied to any point in that column will be available at any other point along the same column.

These columns are typically used to supply Vcc and GND to the circuit being constructed. Theremaining sockets of the breadboard are connected horizontally, so that a voltage applied to anypoint in a row is available at all other points of the row. Since rows on different sides of the centreisolator are unconnected, the centre region is most commonly used to place integrated circuits(such as op-amps, etc.) so that each pin of the IC has an entire row for possible connections.This wiring configuration applies, not only to the breadboards which we will use in the lab, but ingeneral to most breadboards.

Connectors

You might take note of the fact that the several instruments will have different connectionterminals on the front panels, courtesy of different applications and histories. All of theseconnectors are female connectors, and are identified by Figure 5b. The corresponding male

connectors are identified by Figure 5a. Often it takes a fair amount of patching to connect acrossdifferent species of connectors. The crudest way to do so is to use the alligator clip (see Figure5a). However, the preferred way to connect up a circuit on the breadboard is using single corewire that we will use for most of the experiments.

Figure 5: Connectors

EQUIPMENTS

Resistors 1k X 1

Rectifying silicon diode 1N4001 X 1

Analog multimeter

Digital multimeter

Breadboard

GW GPR3030 DC power supply

Crocodile clips, BNC Connectors, Connection wires (single core)


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Experiment: Part IAnalog and digital multimeter

1. This test is required to calibrate a multimeter before we use it for the first time. Thecalibration process is important to eliminate (neglect) the multimeter's internal resistanceand the lead resistance. Take your analog multimeter and select to X10 ohm scale. Withthe test lead tips touching each other, adjust the null ohm knob (see Figure 1) orsometime called "zero" knob on the front panel so that the needle indicates a resistanceof zero ohms (top scale). Now the analog multimeter is already calibrated.

Figure 1a: Analog multimeter short-lead test

Rshorted = __________

2. Use the same way for digital multimeter. Select to ohm meter range and repeat the test.This time you will hear a buzzer/beep sounds indicating that the leads are shorted eachother.

Figure 1b: Digital multimeter short-lead test

Record the resistance reading from the digital display. This resistance should be verysmall indicating that internal and lead resistances are negligible.

Rshorted = __________


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3. To check a fuse inside digital multimeter for proper operation, touch the leads together asshown below. Note that the leads are now changed.

Figure 1c: Digital multimeter fuse test

Record the resistance reading from the digital display.

Rfuse = __________

4. Configure the multimeters (analog and digital) to measure the resistance of a givenresistor (Brown-Black-Red). This configuration is selected by choosing the appropriatescale for ohm meter reading. For applications which require the specific measurement ofresistance (say a few hundred Ohms), select the desired setting. Record the resistance in

Table 1a.

Table 1a: Readings

Brown-Black-RedAnalog

multimeterDigital

multimeterDifference,

Resistance,

5. Configure the multimeter (analog or digital) to measure the resistance/continuity of allcrocodile clips (alligator clips) inside your workbench. This test is useful for detectingbroken wires in circuits (open circuits). Determine whether the connection is open orshort. If short, the crocodile clip is ok, otherwise it is broken. The broken crocodile clip

should be removed and need to be sent to the technician for repairing.

Number of broken wires = __________

6. Any group which fails to return broken wires (if available) for repairing will get 50%marks deduction. This is considered as a mandatory mistake. You should be alertwith this caution all the time.


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7. Diodes are one of the components that can be tested very easily. Ordinary diodes aswells as Zener diodes can be checked by using a multimeter. While testing a diode theforward conducting mode and reverse blocking mode has to be tested separately.

Figure 1d: Ordinary diode symbol and its polarity

8. To check an ordinary silicon diode using an analog multimeter, put the multimeterselector switch in the ohm meter range. Connect the negative lead of multimeter to theanode and positive lead to cathode of the diode. If multimeter displays some resistancereading, we can assume that the diode is healthy. Repeat the measurement by reversingthe connection and record them in Table 1b.

Table 1b: Diode testing using analog multimeter

Anode Cathode Resistance, Conduction

mode

-ve lead +ve lead

+ve lead -ve lead

9. To check an ordinary silicon diode using a digital multimeter, put the multimeter selectorswitch in the diode check mode. Connect the positive lead of multimeter to the anode and

negative lead to cathode of the diode. If multimeter displays a voltage between 0.5 to 0.7,we can assume that the diode is healthy. This is the test for checking the forwardconduction mode of diode. The displayed value is actually the potential barrier of thesilicon diode and its value ranges from 0.5 to 0.7 volts depending on the temperature.

10. Now connect the positive lead of multimeter to the cathode and negative lead to theanode. If the multimeter shows an infinite reading (over range), we can assume that thediode is healthy. This is the test for checking the reverse blocking mode of the diode.Record them in Table 1c.

Table 1c: Diode testing using digital multimeter

Anode Cathode Voltage, VConduction

mode

+ve lead -ve lead

-ve lead +ve lead


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Experiment: Part IIDC Power Supply

1. This test is required to calibrate a DC power supply before we use it for the first time. Thecalibration process is important to make sure that the voltage output of a supply is exactlythe same with the actual voltage measured by digital multimeter.

2. Use crocodile clips included with male banana connector to perform connection as shownin Figure 2a. To short wire between ve and GND outputs, use a shorting bar or a singlecore wire. Make sure that the power switch is firstly set to OFF position. Set current modeselection to LO position. Set both voltage knob and voltage tuning knob to fully counterclockwise position (CCW).

Figure 2a: Positive output power supply with ground and its schematic

3. Connect the DC power supply output to a digital multimeter. Configure the multimeter tomeasure DC voltage. Connect the positive lead of multimeter to the positive output ofpower supply and negative lead of multimeter to the negative output of power supply.

4.

Turn on the power supply and green LED (CV) will light on. If it is not, set the currentknob to a little bit clock wise (CW) direction. Adjust the voltage tuning knob (FINE) untilyou get almost 0 V displayed on the digital multimeter screen. Adjust the X screw as inFigure 2a so that the voltage range is exactly display 0 volt. Now the power supply isalready calibrated.

5. Advance the voltage slowly by adjusting the voltage knob and confirm your readings asyou fill up Table 2a.


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Table 2a: Readings

Voltage displayed bypower supply panel, V

Voltage displayed bydigital multimeter, V

Difference, V

2

5

10

12

15

25

6. Turn off the power supply.

7. Construct the connection as shown in Figure 2b. Now you are shorting the +ve and GNDoutputs. Connect the positive lead of multimeter to the negative output of power supplyand negative lead of multimeter to the positive output of power supply.

Figure 2b: Negative output power supply with ground and its schematic


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8. Turn on the power supply and slowly advance the voltage by adjusting the voltage knoband confirm your readings as you fill up Table 2b.

Table 2b: Readings

Voltage displayed bypower supply panel, V

Voltage displayed bydigital multimeter, V

Difference, V

2

5

10

12

15

25

9. Show how you build the following power supplies based on the given schematic. Use twounits of GW GPR3030 to do this. Measure the equivalent voltages.

Figure 2c: Two power supplies and the symbol

VA = __________V, Vx = __________V, VAX = __________V


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10. Show how you build the following power supplies based on the given schematic. Use twounits of GW GPR3030 to do this. Measure the equivalent voltages.

Figure 2d: Two power supplies and the symbol

VB = __________V, Vx = __________V, VBX = __________V

11. Show how you build the following power supplies based on the symbol. Use two units ofGW GPR3030 to do this. Measure the equivalent voltages.

Figure 2e: Two power supplies and the symbol

VC = __________V, VX = __________V, VCX = __________V

12. Turn off the power supply and RETURN the connection back to the positive output powersupply as shown in Figure 2a.


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Experiment: Part IIIBreadboard

1. This test is required to check the interconnection between holes on a breadboard asshown in Figure 3a. The test is important so that you familiar with the breadboardconfiguration and later will use for most of the experiments.

Figure 3a: Breadboard

2. Check the continuity of connections as shown in Figure 3b. You may refer Figure 4 in theintroduction part to ease you in determining the internal connection of a breadboard. Themultimeter might be useful for checking the connection. Record your results in Table 3a.

Figure 3b: Breadboard connections


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Table 3a: Results

Nodes Continuity ( or X)

A and B

A and D

A and E

D and E

D and G

E and G

G and H

A and Z

A and Y

X and Y

X and W

X and R

V and U

U and S

P and Q

O and P

M and N

M and L

I and K

I and J

L and F

C and F

C and Y

R and T


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REVIEW QUESTIONS

1. List the uses of multimeter, breadboard and power supply.

2. What are the differences between analog and digital multimeter.

3. Indicate how a diode conducts or does not conduct when a digital/analog multimeter isapplied to it.

4. Why it is important to learn about different output polarity of a DC power supply.

TURN IN ONE REPORT PER GROUP AT THE END OF YOUR LAB SESSION.THERE IS NO TAKE HOME REPORT.

Documents

Exp 1 Multimeter,Breadboard and Power Supply (2012)