Experiment 1 Introduction to Electronic Test Equipment W T Yeung and R T Howe UC Berkeley EE 105 Fall 2004 1 0 Objective In this experiment you will become familiar with some of the test equipment in the laboratory and will become reasonably adept at using the HP 54615B oscilloscope to perform DC and transient measurements 2 0 Procedure 2 1 Oscilloscope and Signal Generator 1 Insert a 1 kHz 5 V p p peak to peak square wave into the first input Ch1 Set that channel for AC coupling The waveform should be 5 divisions high on the 1V div scale If the waveform looks very distorted adjust the probe using a screwdriver Lab Tip The probes that come attached to the oscilloscopes are 10x probes Readings should be read from the 10x markings All other cables are 1x cables and results should be read using the 1x markings 1 of 9 Procedure FIGURE 1 Effects of adjusting the Probe Adjust screw on test waveform Note that adjustment is not normally necessary Undercompensated Probe Adjust Overcompensated Correct 2 Repeat these steps for the second channel Ch2 3 Now connect a DC power supply to the vertical input and vary its voltage Check the accuracy of the panel meter on the power supply using the scope readings What is the maximum voltage the supply will produce How accurate is the power supply s panel Can this experiment be done with the vertical input on AC mode why or why not What is the difference between DC and AC coupling Hint To display a DC signal using the oscilloscope perform the following a Apply 0V to the probe b Set Volts Div to 2V c Position the sweep on the screen and then apply the DC voltage DO NOT hit autoscale Autoscale is good for any type of signal but DC 4 Now connect the HP 8116A signal generator to the vertical input Set the generator to an arbitrary frequency and determine the accuracy of the generator s display by comparing the period of the sinusoid on the scope with the period of the sinusoid on the display Play around with different frequencies and amplitudes How closely do the two measurements agree What is the maximum peak to peak amplitude available from the generator The minimum Vary the TRIGGER LEVEL control and note the effect on the waveform What is happening 5 Set the generator to output a pulse Compare the period and frequency readings on the generator controls to those actually observed on the scope What is the shortest 2 of 9 Experiment 1 Introduction to Electronic Test Equipment Procedure pulse width in seconds that you can generate The longest Note that this may depend on the frequency 2 2 Triggering Unless specified otherwise set the triggering source to the input you are examining and use auto triggering Lab Tip You will always be using the HP 8116A in Normal Mode The unit saves the settings each time it is turned off To ensure that the signal generator is operating properly make sure The following lights are OFF AUTO LIMIT COMPL and DISABLE Always operate the generator with the AMP and OFS instead of HIL and LOL DTY setting should be 50 All other lights should be off for further explanation see the HP 8116A manual Experiment 1 Introduction to Electronic Test Equipment 3 of 9 Procedure 2 3 The Digital Multimeter 1 Construct the circuit below Let VSupply be 10V FIGURE 2 Simple Resistive Divider Circuit V 1 RA 10 k VSupply V 2 RB 20 k 2 Use the digital multimeter to determine the voltages at nodes 1 and 2 3 Derive a relationship for V 2 in terms of VSupply RA and RB 4 Calculate the current through resistor RB Measure the current with the digital multi meter How do the results compare Lab Tip Cables for the digital multimeter can be connected to it from both the front and the rear This allows for quick voltage and current measurements by simply switching between the Front Rear button 5 Beware of the hazards of the current mode The resistance across the multimeter is nearly a short circuit in this mode What happens if you connect an ideal ammeter across the terminals of a voltage source DON T DO IT Discuss this point with your TA if you don t understand the concepts 2 4 Resistor I V 1 Using the digital multimeter DMM measure the resistance on a 10 k carbon resistor 2 Carefully plot the resistor s I V characteristic using the oscilloscope and DMM Label all relevant points Refer to pages 8 9 to learn how to perform an I V using the oscilloscope Vsupply should be an AC source i e sine wave 4 of 9 Experiment 1 Introduction to Electronic Test Equipment Procedure 2 5 Transient Analysis 1 Construct the following R C circuit You should have seen this circuit many times in your introductory circuits course FIGURE 3 Lowpass Filter Circuit 10K vout vS 0 01 F 2 Let vs be a square wave with a frequency of 1kHz and a 50 duty cycle 3 Place channel 1 of the oscilloscope at vs and channel 2 at vout 4 Display both waveforms on the oscilloscope Sketch the waveforms and label all the relevant points 5 Repeat step 2 with frequencies of 100 Hz 10 kHz and 100 kHz Experiment 1 Introduction to Electronic Test Equipment 5 of 9 Appendix 3 0 Appendix 3 1 Breadboard Basics FIGURE 4 Layout of breadboard Fig 5 has wiring Two vertical buslines in center are omitted Busline Busline Same node Same node NOT at same voltage The breadboard is where you will be doing most of your work in lab Here are some points to remember The buslines are at the same voltage vertically The top half of the busline is not at the same voltage as the bottom half You should use a jumper if you intend to work on both halves of the board The central sections of the breadboard are at the same voltage horizontally Shown below is the metal network for the breadboard 6 of 9 Experiment 1 Introduction to Electronic Test Equipment Appendix FIGURE 5 Metal Connections within the Breadboard Metal Line When wiring it is important to keep your work neat This discipline will save time for you and your TA in debugging when your circuit doesn t work Below are some tips Keep your wires short Do not loop wires over the chip Use the buslines for Ground or a DC supply voltage e g VCC Sometimes you can get cleaner signals if you short the metal base of the breadboard to the circuit s ground Figure 6 shows identical connections using good and bad wiring techniques Note how the resistor on the good side does not loop over the chip Instead it gets from point A to B by making manhattan 90 degrees turns along unoccupied sections of the breadboard Experiment 1 Introduction to Electronic Test Equipment 7 of 9 Appendix FIGURE 6 Proper and
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