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Measuring Instruments
Prepared by:Dharmendra Sadhwani
Assistant ProfessorEC department SISTec-E
SISTEC-E
Constructing a Series Circuit◦ Ohm’s Law Review◦ Breadboard Overview◦ DC Power Supply Review
Measuring the D.C. Voltage in the Series Circuit◦ Multimeter Overview
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Objectives
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Determine the current
Use Ohm’s Law: V = I x R
3V = I x 1000 Ω
Solve for I: I=3V / 1000 Ω =
3milliAmps
Today we will build this series circuit
3V
0V
R = 1K Ω
I = ? Amps
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1)A 1K Ohm Resistor2)Breadboard3)DC Voltage Source4)2 sets of Banana Clip
to mini-grabber wires
How to Build the Circuit
We need 4 components
3V
0V
R = 1K Ω
I = 3mA
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The Breadboard
The breadboard is used to build circuits without the need of soldering
You can plug resistors and wires right into the board
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The Breadboard
The left and right side columns are connected horizontally shorted
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IDG
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The columns between the blue and red bars crossing the bridge are vertically shorted
The
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The The left and right side columns are
connected horizontally shorted
The columns between the blue and red bars crossing the bridge are vertically shorted
The Breadboard
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Setting up the breadboard
Plug 1 end of the 1K resistor in the top row, on the left side of the bridge
Plug the other end of the 1K resistor in the top row, on the right side of the bridgetor into the top row, on the right side of the bridge
of the resistor into the top row, on the right side of the bridge
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This DC Power supply is capable of generating voltages from -25V to 25V.
For this lab, we will be using the 6V supply terminals.
First, press the Power Button to turn it on.
Setting Up the DC Power Supply
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Press Output On/Off once to turn on the output.
Press the +6V button to tell the power supply that we want to alter the output from the 6V terminals.
Once done, your screen should look the same as it does on this slide.
Setting Up the DC Power Supply
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Use the dial to increase the display value to 3 volts as shown.
Note: You can safely ignore the value of the right most digit for this experiment.
Once you have reached 3V, Press Output On/Off once to turn the output OFF while you hook up the circuit.
Setting Up the DC Power Supply
This is the digit we want to adjust
Press this arrow toSelect the
desired digit
Rotate this dial toalter the output value.
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Plug the ‘banana’ end of your cables into the 6V terminals of your power supply
Connect the mini-grabber ends of the cables around your 1K resistor on the breadboard
After attaching the mini-grabbers to your circuit, press the Output On/Off to apply 3 Volts across your 1K resistor
Connecting the Power Supply to your Circuit
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Measuring the Voltage Across the Resistor…Using the Multimeter
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What is a Multimeter?
A tool capable of measuring a variety of different quantities.
Possible Measurements◦ Current (Amperes)◦ Resistance (Ohms)◦ Voltage (Volts)
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How is the Multimeter different than the Oscilloscope?
Numerical Output Displayed
Represents a complete signal with a single value.
Measures voltage, current and resistance.
Graphical Output Displayed
Shows how a signal changes over time
Many only display voltage
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Multimeter Oscilloscope
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Explanation of ControlsSetting up the multimeter for various measurements.
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Taking measurements with the Multimeter
First, we connect our wires.
One wire is always connected to the black terminal. This is called the common terminal.
The red terminal is used when measuring voltage, resistance and small currents.
The white terminal is used when measuring large currents.
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Taking measurements with the Multimeter
Next, we turn it on and select the item to measure. Choose from:
◦ Current◦ Resistance◦ Voltage
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Power Button
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Taking measurements with the Multimeter
Now, we select our scale. Either select a scale appropriate for your measurement or
choose AUTO and let the multimeter select the appropriate scale for you.
Measuring the voltage from across the 1K resistor (~3V), you wouldn’t want to choose 200mV (much too small) or 200V (much too large). Instead, the 2V selection is more suitable.
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Taking measurements with the Multimeter
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While your circuit is attached to the power supply…
Attach the minigrabber end around the 1K resistor
Press the “POWER” button on the multimeter and take a reading!!
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Building & Verifying Series Circuit #2
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3V R2 = 1KΩ
0V
R1 = 1KΩ
Ohm’s Law States:
V(R1) = 1.5mA x 1K Ω = 1.5V
V(R2) = 1.5mA x 1K Ω = 1.5V
We are now going to build the circuit, and verify the voltage drops…
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Resistors connected by only 1 terminal, back-to-back, are considered to be in ‘seriesOhm’s Law States:
V(R1) = 1.5mA x 1K Ω = 1.5V
V(R2) = 1.5mA x 1K Ω = 1.5VWe are now going to
build the circuit, and verify the voltage drops…
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Setting up the breadboard
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Turn off the 3V supply and disconnect the cables
Disconnect the cables to the minigrabbers to the multimeter
Obtain a 2nd 1K resistor
Plug one end of the resistor into a hole in the same row as the end of the other resistor
Plug the other end into a hole in another row
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Turn off the 3V supply and disconnect the cables
Disconnect the cables to the minigrabbers to the multimeter
Obtain a 2nd 1K resistor
Plug one end of the resistor into a hole in the same row as the end of the other resistor
Plug the other end into a hole in another row www.sistec.ac.in
Taking measurements with the Multimeter
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Set the Power Supply to 3V
Attach the power supply leads as follows
Measure the voltage across each resistor with the multimeter
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Resistors in Parallel
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Resistors connected at 2 terminals, sharing the same node on each side, are considered to be in ‘parallel’
3V
0V
R1 = 1K Ω
The voltage is the same on both branches of the circuit
The current will split!
It is now up to you to build this circuit and verify the voltages
R2 = 1K Ω
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Including a Diode In the Circuit
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We’ll use LEDs (Light Emitting Diodes) for our circuits.
3V R1
= 1
KΩ
0V
Unlike resisters, the two diode leads (wires) must be connected in the correct way.
The longer lead (anode) should be connect so that current flows through it and to the shorter lead (cathode).
Note: In some diodes, a stripe is used to indicate the cathode lead. Round diodes often have a flat side, indicating the cathode.
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Your Turn1) Build the parallel circuit (in the last slide) and measure
the voltage across it◦ Using Ohm’s Law, what is the current through each
resistor?◦ What is the total current in the circuit?
2) In your parallel circuit, change one of the 1K resistors to a 2K resistor◦ Measure the voltage across each resistor◦ Use Ohm’s law to determine the current through each
resistor3) Rebuild the two resistor series circuit…
◦ Change one of the 1K resistors to a 2K resistor◦ Measure the voltage across each resistor◦ Use Ohm’s law to determine the current through each
resistor
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Your Turn4) Build a circuit with a diode in series with a 1K resistor
◦ Using Ohm’s Law, what is the current through the resistor?◦ What is the total current in the circuit?◦ Reverse the anode and cathode connections of the diode
and observe the results.
5) Build a circuit with a diode in series with 2 parallel 1K resistors
◦ Measure the voltage across each resistor◦ Use Ohm’s law to determine the current through each
resistor
6) Don’t forget the HW!
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Digital Multimeter
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What is a Digital Multimeter?A digital Multimeter measures AC / DC
voltage, resistance, and current in an electric circuit. It is highly accurate and displays an LCD number readout.
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Test leads are used to connect the multimeter to the circuit to be tested.
Test Leads
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Function/Range Switch
DC Voltage
Battery Test
DC Current
AC Voltage
Resistance
Continuity Test
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Voltage Meter The voltmeter is used
to measure the voltage potential across a component in an active circuit.
It can be used to measure either DC or AC voltages.
AC voltage can ONLY measure sinusoidal (SINE) waveforms.
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Test Lead Connections - Voltage
Plug the RED test lead into the jack labeled V/ and the test lead into the jack labeled COM (common).
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The ohmmeter is used to measure the resistance of a component.
POWER CANNOT be applied to the component being tested.
The ohmmeter actually applies a small voltage and uses Ohm’s law to calculate the resistance from the measured current.
Ohmmeter
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Test Lead Connections - Resistance
Same as voltage measurement
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AmmeterThe ammeter is used to measure the current through a component in an active circuit.
It can be used to measure only DC current.
Some multimeters can also measure AC current.
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Test Lead Connections - Current
Plug the RED test lead into the jack labeled mA for milliamps or into the jack labeled 10A for circuits with high current levels. Plug the BLACK test lead into the jack labeled COM.
Be certain to select the range according to the test lead connections.
Observe proper polarity.
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Be sure the test leads are connected appropriately for the intended measurement.
Turn the meter’s Function/Range switch to the function (ACV, DCV, DCA or ) to be measured.
Select a range which is higher than the expected value.
Connect the test leads to the circuit/component being tested. Observe proper polarity.
Turn the meter’s Function/Range switch to reduce the range and increase the accuracy.
Record results. Remember to turn the power OFF when finished.
Basic Instructions
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Special FunctionsContinuity Tester
Used to test the continuity between two points. Will produce an audio tone.
Diode Tester
Used to test the resistance in a diode for forward bias and reverse bias.
Battery Tester
Used to test 9 volt and 1.5 volt (AAA,AA, C, D) batteries.
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Check meter’s battery Review instructions to make sure all the
meter’s settings are accurate for the type of testing being conducted
Check to see if test leads are broken or not connected properly
Inspect and test the fuse
If the Meter Malfunctions :
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Function Generator
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Introduction
A function generator is used in many engineering fields to generate a wide variety of synthesized electrical signals such as the sine, square, triangle and ramp functions. These signals are used for testing and diagnostic applications.
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THANK YOU