I NEED YOUR HELP!! Setting the function generator to High Z mode or a specific l
ID: 1715253 • Letter: I
Question
I NEED YOUR HELP!!
Setting the function generator to High Z mode or a specific load impedance, is called impedance matching, and is a critical feature in electrical design. Review the two articles on impedance matching listed below and answer the following questions: http://www.j aycar.com/images_uploaded/impmatch.pdf http://www.effectivebits.net/2011/12/whats-wrong-with-my-function-generator.html Why is the measured voltage using the oscilloscope greater than expected if the function generator is not in High Z mode? Why is it necessary to enter the load impedance into the function generator, if the load is not a high impedance, e.g. a 10 Ohm load?Explanation / Answer
(a) Output to "High Z" too makes the voltages shown coincide.
to generate 5 V across a 50 ohm load, with its internal resistance also 50 ohms, the sig. gen. actually generates 10 V of which, because the two 50 ohms in series act as a voltage divider, only 5 v appears at the output terminals, and that is the value that is displayed on the sig. gen. panel. If a high impedance load such as an oscilloscope is attached, then the voltage divider is distorted, with a very small drop across the sig. gen.'s internal 50 ohms, and very nearly all across the 'scope input. The sig.gen. does not "know" this and still gives the same display as for the 50 ohm load. As , there is a "High Z" setting it replaces the internal impedance with a high impedance to match the load, so the voltage divider effect is restored.
(b) output resistance of the function generator has a value of 10 Ohm. This implies that the actual output voltage one measures over the load will vary with the load resistance because of the voltage divider. The output amplitude is calibrated for a 10 Ohm load resistance, which means that the voltage shown on the function generator's display panel corresponds to the actual voltage VLOAD over the load only when the load is equal to 10 Ohm. Thus, be careful when applying the output voltage of the function generator to a circuit whose input resistance is different from 10 Ohm. In general, it is a good practice to measure the amplitude of the waveform using a Digital Multimeter (DMM) or an oscilloscope instead of relying on the function generator display reading.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.