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lab 2 2009 instrumentation - bioelectrode impedance

# lab 2 2009 instrumentation - bioelectrode impedance - LAB 1...

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L AB 1: R EVIEW OF LABORATORY PROCEDURES R ESISTIVE C IRCUITS – B IOELECTRODE IMPEDANCE I Purpose This laboratory has two objectives: 1 to get you organized for the BME 302 laboratories and reacquainted with the equipment you will be using. Two basic resistive circuits (voltage divider, Wheatstone bridge) are used to illustrate the use of the equipment. The circuits are important in their own right. 2 To investigate a method for measuring experimentally the impedance of a bioelectrode and examine the effect of frequency on the impedance. It is very important that you remember from this lab the main features of the lab equipment because otherwise, you may find it difficult to perform the next laboratory experiments of the semester. II Oscilloscope and Waveform generator Prelab: There is no prelab for this section. Procedures: 1. Connect the output of the waveform generator to display the waveform on channel 1 of the oscilloscope. 2. Adjust the waveform generator to deliver a 1000 Hz, 1 V peak amplitude sinusoidal waveform. 3. Adjust oscilloscope vertical gain on channel 1 to fill the display with the waveform; adjust the time base so that two cycles of the waveform are shown. Note in your report the volt/div and sec/div settings. Relate to the amplitude and period of the waveform. 4. Display using the “measure” function and read the amplitude of the waveform on the display while the scope is set to dc; switch the scope to ac and read the amplitude again. In your report, explain the ac/dc setting when used with high-frequency waveforms? 5. Return the scope to dc. Decrease the frequency of the sinusoidal waveform to 10 Hz. Readjust the time base to show two cycles of the waveform. Note the sec/div setting. Relate the sec/div setting selected when the frequency is 10 Hz to that selected when the frequency was 1000 Hz. 6. Read the waveform amplitude with the scope set for dc and for ac. In your report, explain the ac/dc setting when used with low-frequency waveforms and contrast with what you saw in item 4? 7. Return the frequency to 1000 Hz and readjust the volt/div and sec/div settings as in 3. Set the scope trigger to “ch 1” and observe the behavior of the waveform. It should appear “frozen” on the display. Move the trigger level marked by the arrow on the right side of the display to higher 1

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values until the waveform scrolls. Read on the oscilloscope the trigger level for which the waveform switches from “frozen” to “scroll”. Move the trigger level marked by the arrow on the right side of the display to lower values until the waveform scrolls. Read on the oscilloscope the trigger level for which the waveform switches from “frozen” to “scroll”. Discuss in your report the effect of the trigger level adjustment.
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lab 2 2009 instrumentation - bioelectrode impedance - LAB 1...

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