Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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SEMICONDUCTOR LAB.
Lesson 1: NI ELVIS II Workspace Environment
The NI ELVIS II environment consists of the following components:
Hardware workspace for building circuits and interfacing experiments
NI ELVIS II software (created in NI LabVIEW software), which includes
the following:
• Soft Front Panel (SFP) instruments
• LabVIEW Application Programmatic Interface (API)
• Multisim Application Programmatic Interface (API)
With the APIs, you can achieve custom control of and access to NI ELVIS II workstation
features using LabVIEW programs and simulation programs written within Multisim.
Figure 1-1. NI ELVIS II Workstation
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Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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Goal
This lab introduces NI ELVIS II by showing how you can use the workstation to measure
electronic component properties. Then you can build circuits on the protoboard and later analyze
them with the NI ELVIS II suite of SFP instruments.
This lab also introduces the operation of themistor.
Required Soft Front Panels (SFPs)
• Digital Ohmmeter DMM[Ω],
• Digital Capacitance Meter DMM[╫ ]
• Digital Voltmeter DMM[V]
• Variable Power Supply (VPS)
Required Components
• 1.0 kΩ resistor, R1, (brown, black, red)
• 2.2 kΩ resistor, R2, (red, red, red)
• 1.0 MΩ resistor, R3, (brown, black, green)
• 10 kΩ resistor, R1, (red, black, orange)
• 10 kΩ thermistor, RT
• 1 µF capacitor, C
Exercise 1-1 Measuring Component Values
1. Connect the NI ELVIS II workstation to your computer using the supplied USB cable. The
box USB end goes to the NI ELVIS II workstation and the rectangular USB end goes to the
computer. Turn on your computer and power up NI ELVIS II (switch on the back of
workstation). The USB ACTIVE (orange) LED turns ON. In a moment, the ACTIVATE LED
turns OFF and the USB READY (orange) LED turns ON.
2. On your computer screen, click on the NI ELVISmx Instrument Launcher Icon or shortcut. A
strip of NI ELVIS II instruments appears on the screen. You are now ready to make
measurements.
Figure 1-2. NI ELVISmx Instrument Launcher Icon Strip
3. Connect two banana-type leads to the digital multimeter (DMM) inputs [VΩ ] and [COM] on
the left side of the workstation. Connect the other ends to one of the resistors.
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Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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4. Click on the DMM icon within the NI ELVISmx Instrument Launcher to select the digital
multimeter.
Figure 1-3. Digital Multimeter, Ohmmeter configuration
You can use the DMM SFP for a variety of operations such as voltage, current, resistance, and
capacitance measurements. Use the notation DMM[X] to signify the X operation.
The proper lead connections for this measurement are shown on the DMM front panel.
5. Click on the Ohm button [Ω] to use the digital ohmmeter function, DMM[Ω]. Click on the
green arrow [Run] box to start the measurement acquisition. Measure the three resistors R1, R2,
and R3.
Fill in the following data:
R1 _______ (1.0 k Ω nominal)
R2 _______ (2.2 k Ω nominal)
R3 _______ (1.0 M Ω nominal)
To stop the acquisition, click on the red square [Stop] box.
Note If you click on the Mode box, you can change the {Auto} ranging to {Specify Range} and
select the most appropriate range by clicking on the Range box.
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Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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End of Exercise 1-1
Exercise 1-2 Building a Voltage Divider Circuit on the
NI ELVIS II Protoboard
1. Using the two resistors, R1 and R2, assemble the following circuit on the NI ELVIS II
protoboard.
Figure 1-4. Voltage Divider Circuit
2. Connect the input voltage, Vo, to the [+5 V] pin socket.
3. Connect the common to the [GROUND] pin socket.
4. Connect the external leads to the DMM voltage inputs [VΩ ] and [COM] on the side of the NI
ELVIS workstation and the other ends across the 2.2 kΩ resistor.
5. Check the circuit and then apply power to the protoboard by pushing the prototyping board
power switch to the upper position [–]. The three power indicator LEDs, +15 V, –15 V, and +5
V, should now be lit and green in color.
Figure 1-5. Power LED Indicators on NI ELVIS II protoboard.
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Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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Note If any of these LEDS are yellow while the others are green, the resettable fuse for that
power line has flipped off. To reset the fuse, turn off the power to the protoboard. Check your
circuit for a short. Turn the power back on to the protoboard. The LED flipped should now be
green.
6. Connect the DMM[V] test leads to Vo and measure the input voltage using the DMM[V]
function. Press [Run] to acquire the voltage data.
V0 (measured) _______________
According to circuit theory, the output voltage, V2 across R2, is as follows:
V2 = R2/(R1+R2) * Vo.
7. Using the previous measured values for R1, R2 and Vo, calculate V2. Next, use the DMM[V] to
measure the actual voltage V2.
V2 (calculated) ________________
V2 (measured) ________________
8. How well does the measured value match your calculated value?
End of Exercise 1-2
Exercise 1-3 Using the DMM to Measure Current
According to Ohm’s law, the current (I) flowing in the above circuit is equal to V2/R2.
1. Using the measured values of V2 and R2, calculate this current.
2. Perform a direct current measurement by moving the external lead connected to [VΩ] to the
current input socket (A). Connect the other ends to the circuit as shown below
Figure 1-6. Circuit Modification to measure Current
3. Select the function DMM[A] and measure the current.
I (calculated) ________________
I (measured) ________________
4. How well does the measured value match your calculated value?
End of Exercise 1-3
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Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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Exercise 1-4 Observing the Voltage Development of an
RC Transient Circuit
Using the DMM[ ] function, measure the 1 µF capacitor.
1. Connect the capacitor leads to the Impedance Analyzer inputs, [DUT+] and [DUT–], found on
the left lower wiring block of a NI ELVIS II protoboard.
2. For capacitance and inductance measurements, the protoboard must be energized to make a
measurement. Switch the protoboard power ON.
3. Click on the capacitor button [ ] to measure the capacitor C with the DMM[ ] function. Press
the Run button to acquire the capacitance value.
C_______(µf)
4. Build the RC transient circuit as shown in the following figure. It uses the voltage divider
circuit where R1 is now replaced with R3 (1 MΩ resistor) and R2 is replaced with the 1 µF
capacitor C. Move your DMM leads to input sockets [V∧ ] and [COM]. The other ends go across
the capacitor.
Figure 1-7. RC Transient Circuit
5. Select DMM[V] and click on RUN.
6. When you power up the circuit, the voltage across the capacitor rises exponentially. Set the
DMM voltage range to {Specify Range} [10 V].
Turn on the protoboard power and watch the voltage change on the digital display and on the
%FS linear scale.
7. It takes about a few seconds to reach the steady-state value of Vo. When you power off the
circuit, the voltage across the capacitor falls exponentially to 0 V. Try it!
Note This demonstrates one of the special features of the NI ELVIS II digital multimeter
it can still be used even if the power to the protoboard is turned off.
End of Exercise 1-4
Study the operation of thermistor RT
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Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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Exercise 1-5 Measurement of the Resistor Component
Values
1. Launch NI ELVIS II.
2. Select digital multimeter (DMM) from the SFP strip of instruments.
3. Click on the Ohm button.
4. Connect the test leads to DMM [VΩ ] and [COM] side sockets.
5. Measure the 10 kΩ resistor and then the thermistor.
6. Fill in the following chart:
10 kΩ Resistor _________________ Ohms
Thermistor _________________ Ohms
7. With the thermistor still connected, place the thermistor between your finger tips to heat it up
and watch the resistance change. It is especially interesting to watch the changes on the display
bar scale (%FS).
The fact that the resistance decreases with increasing temperature (negative temperature
coefficient) is one of the key characteristics of a thermistor.
Thermistors are manufactured from semiconductor material whose resistivity depends
exponentially on ambient temperature and results in a nonlinear response. Compare the
thermistor response with an RTD (100 Ω platinum resistance temperature device) shown in the
following figure.
Figure 1-8. Resistance-Temperature Curve of a Thermistor and an RTD
End of Exercise 1-5
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Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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Exercise 1-6 Operating the Variable Power Supply
Complete the following steps to set a voltage level on one or both of the
variable power supplies.
1. From the strip menu of SFPs, select the [VPS] icon. There are two controllable power supplies
with NI ELVIS II, 0 to –12 V and 0 to +12 V, each with a 500 ma current limit.
Figure 1-9. Virtual SFP for Variable Power Supplies
In the default mode, you can control the VPS with the virtual panel shown above. Set the output
voltage on the virtual knob and click on the [Run] box. The output voltage is shown (blue in
color) in the display area above your chosen power supply. When you click on the stop button,
the output voltage is reset to zero on the protoboard.
Note To sweep the output voltage through a range of voltages, make sure that you have clicked
the [Stop] button. Select the Supply Source (+ or –), Start Voltage, Stop Voltage, Step Size, and
Step Interval, and click on [Sweep].
For manual operation, click on the Manual box and use the knobs on the right side of the NI
ELVIS II workstation to set the output voltages. To view the output voltage in the display area,
click on the white box now appearing next to the LabVIEW label.
2. Connect the leads from the protoboard strip connector sockets labeled Variable Power
Supplies [Supply +] and [Ground] to the DMM voltage inputs.
3. Select DMM[V] and click on RUN. Select VPS front panel and click on RUN.
4. Rotate the virtual VPS control for Supply + and observe the voltage changes on the DMM[V]
display.
Note You can use the [RESET] button to quickly reset the voltage back to zero.
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Tài liệu TN Dụng cụ Bán dẫn – Kit Elvis II
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5. Click on the Manual box to activate the real controls on the right side of the workstation. The
virtual controls are grayed out. Observe that the green LED Manual Mode on the NI ELVIS II
workstation is now lit.
6. Rotate the + voltage supply knob and observe the changes on the DMM.
Note VPS– works in a similar fashion except the output voltage is negative.
End of Exercise 1-6
Exercise 1-7 A Thermistor Circuit
Complete the following steps to build and test the thermistor circuit.
1. On the workstation protoboard, build a voltage divider circuit with the 10 kΩ resistor and a
thermistor. The input voltage is wired to [Supply +] and [Ground] sockets. The voltage across
the thermistor goes to the DMM[V] leads.
Figure 1-10. Temperature Measuring circuit using a Thermistor
Figure 1-11. Real Thermistor circuit on NI ELVIS protoboard
2. Make sure the Variable Power Supply voltage levels are set to zero.
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Apply power to the protoboard and observe the voltage levels on the DMM display. Increase the
voltage from 0 to +5 V. The measured voltage across the thermistor, VT, should increase to
about 2.5 V.
3. Reduce the power supply voltage to +3 V. This ensures that the self-heating (Joule heating)
inside the thermistor does not affect the reading of the external temperature.
4. Heat the thermistor with your finger tips and watch the voltage decrease.
You can rearrange the voltage divider equation to calculate the thermistor resistance as follows:
RT = R1 * VT /(3 –VT)
At an ambient temperature of 25 °C, the thermistor resistance should be about 10 kΩ.
With this equation, called a scaling function, you can convert the measured voltage into the
thermistor resistance. You can easily measure
VT with the NI ELVIS II DMM or within a LabVIEW program (VI).
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