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1 MEASUREMENTS AND INSTRUMENTATION LAB #1: Introduction to Electronic Instrumentation Equipment: DC Power Supply (Lambda LP-411A-FM) Digital Multimeter (FLUKE 8050A) Function Generator (Tektronix CFG250) Oscilloscope (Tektronix 2211) Battery Resistor box Objectives: The purpose of this laboratory is to acquaint you with several of the electronic instruments that you will be using routinely in future labs. You will be asked to use these instruments to perform a number of simple measurements, but you will not always be given step-by-step instructions on how to use them. Rather, you are expected to use the operating manuals that come with each instrument to educate yourself. Use the manuals as a guide, but do not be afraid to intelligently “knob-twist." Your lab instructor will remind you of several simple measures to protect the equipment. At the end of this experiment, you should have gained considerable facility in using these very useful instruments. Procedure: In a lab notebook (not loose-leaf) record your measurements and answer all the questions posed in the lab handout (labeled as “Q”). Use the paragraph subsection numbers 1.1, 1.2, etc. in your notebook record. 1 Digital Multimeter This device is a real “jack of all trades”; it will be as useful as an extra pair of hands when you begin to take measurements. It measures electrical voltage, current, or resistance. 1.1. Look up the specified multimeter accuracy for DC voltage readings. Q: What is it for resistance readings? Q: Within what accuracy will the instrument measure a DC signal of 100 mV? Q: Within what accuracy will the instrument measure an AC signal of 100 mV at a frequency of 100 Hz? Q: Within what accuracy will the instrument measure a resistance of 1000 ohms?2 1.2. Measure the voltage of a battery. Reverse the leads and observe what the meter does. This polarity indication is a nice feature of the meter. Analog meters will “pin out" if the wrong polarity is used, and this can cause damage to this type of instrument. Q: How much current were you drawing from the battery in #1.2? (Hint: Check the impedance specifications for a DC voltage measurement.) 1.3. Connect the multimeter to the + and - terminals on the DC power supply. Set the current-limiter knob at 12 o'clock, turn both voltage knobs full CCW, and switch the unit on. With the meter on the 2-VDC range, slowly increase the coarse voltage control of the power supply. Q: What happens when the voltage exceeds 2V? (N.B.: It is a good practice when measuring a completely unknown voltage to start out on the highest range and move downward until the desired resolution is obtained. Try this with the voltage control turned up a little higher.) 1.4. Turn the vernier (fine) voltage knob on the power supply full CCW and measure the voltage. Then turn it full CW. Q: What is the range of fine voltage control for the power supply? Q: How does your measurement compare with the power supply specifications? Measure the voltage from the + terminal to ground, and from the − terminal to ground. 1.5 Measure the resistance of each of the five resistors in the resistor box and record the measured resistance values along with the color code for each. Q: Are all of the resistors within the tolerance indicated by the color code? 2 Function Generator This instrument produces a variety of voltage wave shapes (e.g., square wave and sine wave) of various amplitudes and frequencies; it has many uses in measurement systems. 2.1. Set the “Amplitude" knob, the “DC Offset" knob, and the “Duty" knob at their center positions. From the FUNCTION section, select the sine wave. Push in the 100-Hz knob to give a 100-Hz sine-wave voltage with zero DC offset (to be discussed later). Connect the multimeter to the MAIN output, and set the multimeter to read AC volts. Determine the maximum output voltage available from the function generator by using the multimeter. Q: How does this compare with the value you obtained in question #2.1?3 2.2. Switch the function generator to 10 Hz, then to 1 Hz, then to 0.1 Hz, leaving the output level fixed. Record the observed voltage readings. Q: What did you find? Discuss your observations with the lab instructor and write down an explanation. Go back to 100 Hz and set the voltage output level to 1 volt, as read on the multimeter, and set the DC OFFSET knob to zero. You will look at this signal on the oscilloscope. 3 Oscilloscope The oscilloscope or “scope" is the basic instrument for dynamic measurements. The virtue of this instrument lies in its tremendous flexibility. It can be used to observe signals ranging in amplitude from a fraction of a millivolt to hundreds of volts at speeds from nanoseconds (10-9) to as much as minutes. A great many things can be done with a scope. We will not go into great detail in this experiment. Additional techniques will be picked up from the future experiments. In ASE369K we will use both an instrument-type oscilloscope (Tektronix 2211) and a “virtual oscilloscope," which is based on the LabView software package. In LAB 1 you will only use the TEK scope. 3.1. Your oscilloscope has, in general, four major sections, which control the operation of the instrument. They are the “amplitude" control section, the “time" control section, the “trigger" control section, and the “cursor and acquisition" control section. There are many other minor knobs controlling various functions such as the intensity of beams, focus, etc. Your instructor will identify them for you. 3.1a. The first section is the “Vertical Amplitude" section, into which the outside signals are fed. Your scope has two channels (CH-1, CH-2) to receive outside signals. Set the MODE switches (three of them) to CH-1, NORM, and CHOP. Turn the voltage control knob for CH-1 to 0.5 volt/div. (Be sure that the small calibration knob is fully CW and that the grey switch below the voltage dial is in the AC position.) 3.1b. The second section is the “Time" control section. Set the SEC/DIV knob to 5 ms (be sure that the small calibration knob is fully CW), and then center the horizontal <− POSITION −> knobs (COARSE and FINE). 3.1c. The third section is the “Trigger" control section. Set the MODE switch to AUTO. Set the SLOPE switch up (i.e., a “+" slope), and center the LEVEL knob. Set the SOURCE switches to CH-1, and LINE, and the


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UT ASE 369K - MEASUREMENTS AND INSTRUMENTATION

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