The DMM gave quite a stable reading up to 3 4 significant figures for Vrms

The dmm gave quite a stable reading up to 3 4

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The DMM gave quite a stable reading up to 3-4 significant figures for Vrms which was 0.932V. Overall the readings correlated as our DMM and generator values were in close agreement with our oscilloscope values. . The generator and the oscilloscope frequencies were the same (20KHz) which verified eq. 1.4. The calculated Vrms value from oscilloscope was within 0.75% of our DMM Vrms value which verified eq. 1.6.
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Figure 2. 1000Hz square wave 3. 1Hz Sine wave: For this wave, adjusting the frequency to the desired value (1Hz) on the generator was slightly harder than the other cases as the frequency was very low so there was more room for error. We finally produced a wave of 1.1Hz frequency. After generating a wave of 1Hz, we proceeded to calculate the signal period (Eq. 1.4). The value for the period was 0.909s. We then grounded the signal on the oscilloscope. Upon adjusting the volt/division and time/division knobs of the oscilloscope, we got time period = 0.9s, voltage Vmax = 0.07V and Vpp = 0.14V. We then calculated Vrms = 0.0425V (Eq. 1.6). The DMM kept generating a series of random numbers for the value of Vrms and was highly unstable. The readings from this are completely inaccurate because the period of the function is too long compared with the fixed sampling rate of the DMM. Therefore in this case, the DMM could not produce an acceptable value due to the low frequency of the wave. Another interesting aspect in the analysis of this wave was the large difference in AC and DC value which had not been witnessed in previous waves. (refer to A.3 under results and discussions for further explanation). Since there was no acceptable Vrms reading from the DMM
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for this wave, we could not verify the calculated Vrms reading. Figure 3 .Sine wave 1 Hz (Volts/S) 4. 2MHz sine wave: For this wave, adjusting the frequency to the desired value (1000Hz) on the generator was fairly accurate and easy as we got the exact frequency. After generating a wave of 20MHz, we proceeded to calculate the signal period (Eq. 1.4). The value for the period was 0.5µs. We then grounded the signal on the oscilloscope. Upon adjusting the volt/division and time/division knobs of the oscilloscope, we got time period = 1ms, voltage (Vmax) = 0.90V and Vpp = 1.8V. We then calculated Vrms = 0.636V (Eq. 1.6). Our AC and DC values for voltage (Vpp) were exactly the same (1.8V). The DMM reading for the voltage was very unstable around 3.1mV. This is within 20416.2% of Vrms so the error approaches infinity. Obviously this is a completely unacceptable reading. The readings from this are completely inaccurate because the period of the function is too short to compare with the rate of the fixed sampling rate of the DMM. Therefore in this case the DMM was useless due to the high frequency of the wave. Since there was no acceptable Vrms reading from the DMM for this wave, we cannot verify eq.1.6. Our AC and DC values for voltage (Vpp) were exactly the same (1.8V).
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