1_Postlab

1_Postlab - ME 365 To: From: Re: Date: POST-LAB EXERCISE...

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ME 365 POST-LAB EXERCISE FOR LABORATORY 1 FALL 2011 1 To: ME365 Student From: Andy Dufresne, Ellis Corp. Re: Digital Multimeters Date: January 18, 2011 1. RMS value of a sine wave with DC offset As we discussed briefly on the phone, we are having some difficulty understanding readings from a DMM. First, we couldn’t figure out how a DMM calculates RMS value of a sine wave with DC offset. When we applied an input of , our DMM displayed the RMS value of 3.674 V. However, when we calculated the RMS value of the input signal by summing the RMS value of the DC component (3 V) and the RMS value of the AC component (3/ = 2.121 V), we obtained 5.121 V. Is our DMM evaluating RMS value accurately or am I making some calculation mistake? To verify the results, we tried to calculate the RMS value of the signal by using the following formula: , where and T is time period ( is the DC offset). After expanding as , we couldn’t finish integration due to the squared sine term. Can you finish the derivation
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1_Postlab - ME 365 To: From: Re: Date: POST-LAB EXERCISE...

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