Tektronix Courseware Academic Labs Sample Labs from Popular Electrical and Electronics Engineering Curriculum March 3, 2014
HalfWaveRectifier -- Overview OBJECTIVES After performing this lab exercise, learner will be able to: Design & build half-wave rectifier circuit Use digital oscilloscope s trigger to capture and display the signal Establish relationship of average & RMS values of a sine and Half- Wave rectified signal Verify the half-wave rectification visually EQUIPMENT To carry out this experiment, you will need: TBS1KB - Digital Oscilloscope from Tektronix PN Junction diode (1N4007 or equivalent), Resistor and capacitor Voltage probe (provided with oscilloscope) / BNC cables Breadboard and connecting wires Signal generator (for providing AC input to rectifier circuit) THEORY Key concepts: A semiconductor diode conducts in only one direction (when forward biased). This property is the basis of a rectifier circuit. A rectifier circuit is used to convert AC to DC signal. PIV Maximum reverse voltage that appears across a reverse biased diode. The reverse voltage should not cross PIV rating of diode otherwise diode is damaged. A half-wave rectifier circuit only converts one half of a cycle of AC input into DC. RMS value of the sine wave is = 0.707 x Vpeak RMS value of half wave rectified output signal is = 0.5 x Vpeak
HalfWaveRectifier -- Procedures Step 1 DUT / SOURCE SETUP Build the circuit as shown below: Choose R = 10k ohms, D = 1N4007 or equivalent diode Switch on the AFG signal to provide input to Diode circuit Set Sine wave of 5Vpk-pk, 1kHz on signal generator / AFG Step 2 EXPERIMENT SETUP Power ON the oscilloscope Connect the Channel 1 probe of the oscilloscope to input of the rectifier Connect the Channel 2 probe to output of the rectifier (across the resistor R) Acquire the signal(s) from circuit on oscilloscope Step 3 Do the Autoset on the scope to efficiently capture and view the signal If AUTOSET feature is not enabled, then manually set the horizontal and vertical scale, and trigger condition to view 3-4 cycles of waveform without any clipping.
Step 4 ADDING MEASUREMENTS Go to measurement menu by pressing MEASURE button on the scope front panel Press CH1 and select MAXIMUM and RMS measurement using Multi-Purpose Knob (MPK) button Add similar measurements for CH2 You can navigate through the measurement list by rotating the MPK knob and select a measurement by pressing it Step 5 Record the measurement values and waveform / screenshot Verify the measurement parameters against designed (calculated based on circuit components) Step 6 CAN YOU ANSWER THIS? Does the diode conduct as soon as the positive half cycle of input starts? Does the RMS value for half wave rectifier output match with theoretical calculation? What is the average (Mean) value of half wave rectified output?
RCLowPassFilter -- Overview OBJECTIVES After performing this lab exercise, learner will be able to: Design & build a 1st order Low pass filter using R & C Use digital oscilloscope s trigger to capture and display the signal Measure amplitude information (Peak to peak value) of the input and output signal Verify the operation of RC low pass filter and estimate the cut-off frequency EQUIPMENT To carry out this experiment, you will need: TBS1KB - Digital Oscilloscope from Tektronix Resistor and capacitor Signal Generator (AFG3K or 2K) Voltage probe (provided with oscilloscope) / BNC cables Breadboard and connecting wires THEORY Key concepts: A filter is a circuit that passes some frequencies and blocks others. The frequency range of input that is passed without any attenuation is known as pass band. The frequency range of the input signal is that is blocked or heavily attenuated is known as stop band. The transition from stop band to pass band or vice versa is known as cut-off frequency. It is the frequency at which the output power is 3dB down (or amplitude is 70.7% of) as compared to power (or amplitude) in pass band. A low pass filter passes the frequencies lower than the cut-off frequncy and blocks frequencies higher that this. The cut-off frequency for RC low pass filter is given by:
RCLowPassFilter -- Procedures Step 1 DUT / CIRCUIT SETUP Build the circuit as shown below: Choose R = 10K, C = 1nF Feed output of the signal generator to V_in (input) of the circuit Select Sine wave of 2Vpp, frequency = 100 Hz Step 2 EXPERIMENT SETUP Power ON the oscilloscope Connect the Channel 1 probe of the oscilloscope to V_in Connect the Channel 2 probe to measure output voltage - V_out Acquire the signal(s) from circuit on oscilloscope Step 3 Do the Autoset on the scope to efficiently capture and view the signal If AUTOSET feature is not enabled, then manually set the horizontal and vertical scale, and trigger condition to view 3-4 cycles of waveform without any clipping. Step 4
ADDING MEASUREMENTS Go to measurement menu by pressing MEASURE button on the scope front panel Press CH1 (channel to be measured) & select PEAK-PEAK and FREQUENCY measurement using Multi-Purpose Knob (MPK) button Select PEAK-PEAK measurement for CH2 as well Step 5 At input signal frequency of 100Hz, record the Pk-Pk amplitude of input and output. Step 6 Keeing the amplitude constant (2Vpp), change the input frequency (AFG signal frequency) to 200 Hz. Record the Pk-Pk amplitude of input and output. Continue increasing the input frequency (AFG signal frequency) in the steps of 100 Hz (till 10kHz) and recording the Peak-Peak amplitude of the output. Step 7 Compute gain = 20 x log (V_out / V_in). Plot the gain Vs. frequency plot. Estimate the cut-off or corner frequency of the circuit by finging a point where gain is -3dB. Step 8 Compare the cut-off frequency value - calculated from RC value against what you actually got from measurement Step 9 CAN YOU ANSWER THIS? When capacitor value is increased, what is the effect on cut-off frequency of the filter?
RCHighPassFilter -- Overview OBJECTIVES After performing this lab exercise, learner will be able to: Design & build a 1st order High Pass filter using R & C Use digital oscilloscope s trigger to capture and display the signal Measure amplitude information (Peak to peak value) of the input and output signal Verify the operation of RC high pass filter and estimate the cut-off frequency EQUIPMENT To carry out this experiment, you will need: TBS1KB - Digital Oscilloscope from Tektronix Resistor and capacitor Signal Generator (AFG3K or 2K) Voltage probe (provided with oscilloscope) / BNC cables Breadboard and connecting wires THEORY Key concepts: A filter is a circuit that passes some frequencies and blocks others. The frequency range of input that is passed without any attenuation is known as pass band. The frequency range of the input signal is that is blocked or heavily attenuated is known as stop band. The transition from stop band to pass band or vice versa is known as cut-off frequency. It is the frequency at which the output power is 3dB down (or amplitude is 70.7% of) as compared to power (or amplitude) in pass band. A high pass filter passes the frequencies higher than the cut-off frequncy and blocks frequencies lower that this. The cut-off frequency for RC high pass filter is given by:
RCHighPassFilter -- Procedures Step 1 DUT / CIRCUIT SETUP Build the circuit as shown below: Choose R = 10K, C = 1nF Feed output of the signal generator to V_in (input) of the circuit Select Sine wave of 2Vpp, frequency = 100 Hz Step 2 EXPERIMENT SETUP Power ON the oscilloscope Connect the Channel 1 probe of the oscilloscope to V_in Connect the Channel 2 probe to measure output voltage - V_out Acquire the signal(s) from circuit on oscilloscope Step 3 Do the Autoset on the scope to efficiently capture and view the
signal If AUTOSET feature is not enabled, then manually set the horizontal and vertical scale, and trigger condition to view 3-4 cycles of waveform without any clipping. Step 4 ADDING MEASUREMENTS Go to measurement menu by pressing MEASURE button on the scope front panel Press CH1 (channel to be measured) & select PEAK-PEAK and FREQUENCY measurement using Multi-Purpose Knob (MPK) button Select PEAK-PEAK measurement for CH2 as well Step 5 At input signal frequency of 100Hz, record the Pk-Pk amplitude of input and output. Step 6 Keeing the amplitude constant (2Vpp), change the input frequency (AFG signal frequency) to 200 Hz. Record the Pk-Pk amplitude of input and output. Continue increasing the input frequency (AFG signal frequency) in the steps of 100 Hz (till 10kHz) and recording the Peak-Peak amplitude of the output. Step 7 Compute gain = 20 x log (V_out / V_in). Plot the gain Vs. frequency plot. Estimate the cut-off or corner frequency of the circuit by finging a point where gain is -3dB. Step 8 Compare the cut-off frequency value - calculated from RC value against what you actually got from measurement Step 9 CAN YOU ANSWER THIS? When resistor value is decreased, what is the effect on cut-off frequency of the filter?
OpampIntegrator -- Overview OBJECTIVES After performing this lab exercise, learner will be able to: Design & build Opamp Integrator circuit Use digital oscilloscope s trigger to capture and display the signal Establish relationship between input and output signal EQUIPMENT To carry out this experiment, you will need: TBS1KB - Digital Oscilloscope from Tektronix Opamp, Resistor and capacitor Voltage probe (provided with oscilloscope) / BNC cables Breadboard and connecting wires Signal generator (for providing AC input to circuit) THEORY Key concepts: An opamp is a high-gain differential amplifier with very high input impedance. OPAMP integrator circuit produces output proportional to integral of its input. If a square wave is input to Integrator circuit, the output will be triangular wave
OpampIntegrator -- Procedures Step 1 DUT / CIRCUIT SETUP Build the circuit as shown below: Switch on the AFG signal to provide input to Diode circuit Set Square wave of 2Vpk-pk, 1kHz on signal generator / AFG Step 2 EXPERIMENT SETUP Power ON the oscilloscope Connect the Channel 1 probe of the oscilloscope to Vin Connect the Channel 2 probe to Vout Acquire the signal(s) from circuit on oscilloscope Step 3 Do the Autoset on the scope to efficiently capture and view the signal If AUTOSET feature is not enabled, then manually set the
horizontal and vertical scale, and trigger condition to view 3-4 cycles of waveform without any clipping. Step 4 ADDING MEASUREMENTS Go to measurement menu by pressing MEASURE button on the scope front panel Press CH1 and select MAXIMUM and MINIMUM measurement using Multi-Purpose Knob (MPK) button Add similar measurements for CH2 You can navigate through the measurement list by rotating the MPK knob and select a measurement by pressing it Step 5 Record the measurement values and waveform / screenshot Verify the measurement parameters against designed (calculated based on circuit components) Step 6 CAN YOU ANSWER THIS? What will be the output of the integrator circuit if the input is a sine wave?
OpampDifferentiator -- Overview OBJECTIVES After performing this lab exercise, learner will be able to: Design & build Opamp Differentiator circuit Use digital oscilloscope s trigger to capture and display the signal Establish relationship between input and output signal EQUIPMENT To carry out this experiment, you will need: TBS1KB - Digital Oscilloscope from Tektronix Opamp, Resistor and capacitor Voltage probe (provided with oscilloscope) / BNC cables Breadboard and connecting wires Signal generator (for providing AC input to circuit) THEORY Key concepts: An opamp is a high-gain differential amplifier with very high input impedance. OPAMP differentiator circuit produces output proportional to integral of its input. A differentiator circuit will generate series of +ve and -ve spikes for square wave input. While triangular wave input becomes square wave at the output.
OpampDifferentiator -- Procedures Step 1 DUT / CIRCUIT SETUP Build the circuit as shown below: Switch on the AFG signal to provide input to Diode circuit Set Square wave of 2Vpk-pk, 1kHz on signal generator / AFG Step 2 EXPERIMENT SETUP Power ON the oscilloscope Connect the Channel 1 probe of the oscilloscope to Vin Connect the Channel 2 probe to Vout Acquire the signal(s) from circuit on oscilloscope
Step 3 Do the Autoset on the scope to efficiently capture and view the signal If AUTOSET feature is not enabled, then manually set the horizontal and vertical scale, and trigger condition to view 3-4 cycles of waveform without any clipping. Step 4 ADDING MEASUREMENTS Go to measurement menu by pressing MEASURE button on the scope front panel Press CH1 and select MAXIMUM and MINIMUM measurement using Multi-Purpose Knob (MPK) button Add similar measurements for CH2 You can navigate through the measurement list by rotating the MPK knob and select a measurement by pressing it Step 5 Record the measurement values and waveform / screenshot Verify the measurement parameters against designed (calculated based on circuit components) Step 6 CAN YOU ANSWER THIS? What will be the output of the integrator circuit if the input is a sine wave?
OpampSchmittTrigger -- Overview OBJECTIVES After performing this lab exercise, learner will be able to: Design & build Opamp Schmitt Trigger circuit Use digital oscilloscope s trigger to capture and display the signal Establish relationship between input and output signal and observe the hysterisis effect EQUIPMENT To carry out this experiment, you will need: TBS1KB - Digital Oscilloscope from Tektronix Opamp and Resistors Voltage probe (provided with oscilloscope) / BNC cables Breadboard and connecting wires Signal generator (for providing AC input to circuit) THEORY Key concepts: An opamp is a high-gain differential amplifier with very high input impedance. OPAMP in open loop mode is used to compare two signals and generate 2 output levels - +Vcc or -Vcc (saturation voltages). Comparators have much faster response than typical Opamps Schmitt Trigger is a comparator with positive feedback. The positive feedback introduces hysterisis effect and reduces the fluctuations in the output that may result due to noisy input. The hysterisis effect (input and output characteristics)
Variation of output with respect to input OpampSchmittTrigger -- Procedures Step 1 DUT / CIRCUIT SETUP Build the circuit as shown below: Choose R1 = 100k, R2 = 10K, Supply Voltage ( +10V ~ 0V ~ -10V)
Switch on the AFG signal to provide input to Schmitt Trigger Set Sine wave of 4Vpk-pk, 1kHz on signal generator / AFG Step 2 EXPERIMENT SETUP Power ON the oscilloscope Connect the Channel 1 probe of the oscilloscope to Vin Connect the Channel 2 probe to Vout Acquire the signal(s) from circuit on oscilloscope Step 3 Do the Autoset on the scope to efficiently capture and view the signal If AUTOSET feature is not enabled, then manually set the horizontal and vertical scale, and trigger condition to view 3-4 cycles of waveform without any clipping. Step 4 Adjust the horizontal scale in such a way that you get to see 2-3 cycles of input sine wave. Press SINGLE to freeze the acquisition - You would see how output is a square wave that toggles between +VCC and -VCC (saturation voltags) Step 5 Turn on TIME cursors, associate them to CH1. Align the cursor 1 on positive transition of output and cursor 2 on negative transition of the output.
Step 6 The voltage reading by Cursor 1 and Cursor 2 are the LTP and UTP respectively. Step 7 Again put the oscilloscope in free run mode Go to Utility > Display > FormatYT > make it XY. Now what you see is the input and ouput response of the circuit. Compare it against the expected. Step 8 CAN YOU ANSWER THIS? What will be the effect on output if input (signal generator) is applied to +ve input of the Comparator and feedback through resistors is given on -ve input?
555AstableMultivibtr -- Overview OBJECTIVES After performing this lab exercise, learner will be able to: Design & build Astable Multivibrator circuit using 555 Timer chip Use digital oscilloscope s trigger to capture and display the signal Measure timing information (period, frequency, T_on, T_off and Duty Cycle) of the signal Verify the designed parameter against actual values using oscilloscope measurement EQUIPMENT To carry out this experiment, you will need: TBS1KB - Digital Oscilloscope from Tektronix 555 Timer IC, Resistor and capacitor (for Astable Multivibrator circuit) Voltage probe (provided with oscilloscope) / BNC cables Breadboard and connecting wires THEORY Key concepts: Period = Time taken by one cycle Frequency = 1/Period Pulse-width modulation (PWM) is a commonly used technique for controlling power to the analog circuits (or electrical device) by varying the pulse width to get specific ON and OFF times. T_on = Period during which the switching devices are switched to conduction state and stays there. T_off = Period during which switching device transits from conduction state to OFF state and stays there The longer the switch is on compared to the off periods, the higher the power supplied to the load is. The DUTY CYCLE is the ratio of ON time to the cycle time (ON time + OFF time). If DUTY CYCLE is 50% then ON and OFF time durations will be same. A PWM signal can be generated using 555 Timer circuit, called as Astable Multivibrator. Frequency and duty cycle can be varied by R and C values.
555AstableMultivibtr -- Procedures Step 1 DUT / CIRCUIT SETUP Build the circuit as shown below: Choose Vcc = 7.5V, RA = 15K, RB= 15K, C = 10nF Switch on the DC power to Timer circuit Step 2 EXPERIMENT SETUP Power ON the oscilloscope Connect the Channel 1 probe of the oscilloscope to pin # 3 of Timer chip Connect the Channel 2 probe to measure capacitor voltage (pin # 2 or 6 of the Timer chip) Acquire the signal(s) from circuit on oscilloscope
Step 3 Do the Autoset on the scope to efficiently capture and view the signal If AUTOSET feature is not enabled, then manually set the horizontal and vertical scale, and trigger condition to view 3-4 cycles of waveform without any clipping. Step 4 ADDING MEASUREMENTS Go to measurement menu by pressing MEASURE button on the scope front panel Press CH1 (channel to be measured) & select PERIOD, FREQUENCY and POS DUTY measurement using Multi-Purpose Knob (MPK) button You can navigate through the measurement list by rotating the MPK knob and select a measurement by pressing it Step 5 Record the measurement values and waveform / screenshot Step 6 Verify the measurement parameters against designed (calculated based on circuit components) Step 7 CAN YOU ANSWER THIS? When capacitor is charging up, what is the output - High or Low? What are the voltage levels, the capacitor charges/discharges between? Can I make a perfect square wave output from a 555 Timer astable multivibrator circuit?
555MonostableMVbrtr -- Overview OBJECTIVES After performing this lab exercise, learner will be able to: Design & build Monostable Multivibrator circuit using 555 Timer chip Use digital oscilloscope s trigger to capture and display the signal Measure timing information (Pulse width / T_on) of the monostable output when triggered Verify the designed parameter against actual values using oscilloscope measurement EQUIPMENT To carry out this experiment, you will need: TBS1KB - Digital Oscilloscope from Tektronix 555 Timer IC, Resistor, capacitor, and a switch (SPST) Voltage probe (provided with oscilloscope) / BNC cables Breadboard and connecting wires THEORY Key concepts: T_on = Period during which the switching devices are switched to conduction state and stays there. Monostable Multivibrator circuit gives a pulse output when triggered. The duration of the pulse depends on R & C value and is given by: T_on = 1.1 x R x C 555 Timer Monostable Multivibrator circuit
555MonostableMVbrtr -- Procedures Step 1 DUT / CIRCUIT SETUP Build the circuit as shown below: Choose Vcc = 7.5V, R = 10K, R2= 10K, C = 100nF Switch on the DC power to Timer circuit Step 2 EXPERIMENT SETUP Power ON the oscilloscope Connect the Channel 1 probe of the oscilloscope to pin # 2 of Timer chip Connect the Channel 2 probe to measure output voltage (pin # 3 of the Timer chip) Acquire the signal(s) from circuit on oscilloscope Step 3 Do the Autoset on the scope to efficiently capture and view the signal CH1 should be DC voltage. If AUTOSET feature is not enabled, then manually set the horizontal and vertical scale, and trigger condition to view 3-4 cycles of waveform without any clipping. Ensure horizontal scale is about 200-500 µs/div Step 4
ADDING MEASUREMENTS Go to measurement menu by pressing MEASURE button on the scope front panel Press CH2 (channel to be measured) & select POS WIDTH measurement using Multi-Purpose Knob (MPK) button You can navigate through the measurement list by rotating the MPK knob and select a measurement by pressing it Step 5 Setup trigger on CH1, falling edge. Press SINGLE button of the oscilloscope now oscilloscope will be ready to acquire signal when a negative edge is found on CH1 Step 6 Record the measurement values and waveform / screenshot Step 7 Verify the measurement parameters against designed (calculated based on circuit components) Step 8 CAN YOU ANSWER THIS? When pin 2 is triggered with negative pulse, what happens to voltage across capacitor? What will be output of the Monostable multivibrator if two consecutive trigger pulses (with a time separation less than T_on) are given to it?