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Setting gain on amp with multimeter
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<blockquote data-quote="jt4x4" data-source="post: 8706010" data-attributes="member: 677386"><p>True RMS doesn't give me desirable results when used to measure the output of variable frequency drives. The current sensors my company uses are not true rms, so they obviously give different readings than a true rms meter. We use current sensors to help troubleshoot pump and fan motors, so I need the numbers to be accurate. For instance: if I see a lower current draw than the motor nameplate states, it could be a broken fan belt or pump coupling. As Fluke explained it to me, it's because variable frequency drives put out a nonlinear load, and the current actually has very high frequency rippling that only a true rms meter can measure, which causes a different measurement between a true rms meter and a non-true rms meter. I responded by asking how that is beneficial when the meter now gives me measurements that don't align with the specs on the motor nameplate, and they said the nameplate is intended for lower non-true rms meters. So for that application, I think true rms is actually a hindrance.</p></blockquote><p></p>
[QUOTE="jt4x4, post: 8706010, member: 677386"] True RMS doesn't give me desirable results when used to measure the output of variable frequency drives. The current sensors my company uses are not true rms, so they obviously give different readings than a true rms meter. We use current sensors to help troubleshoot pump and fan motors, so I need the numbers to be accurate. For instance: if I see a lower current draw than the motor nameplate states, it could be a broken fan belt or pump coupling. As Fluke explained it to me, it's because variable frequency drives put out a nonlinear load, and the current actually has very high frequency rippling that only a true rms meter can measure, which causes a different measurement between a true rms meter and a non-true rms meter. I responded by asking how that is beneficial when the meter now gives me measurements that don't align with the specs on the motor nameplate, and they said the nameplate is intended for lower non-true rms meters. So for that application, I think true rms is actually a hindrance. [/QUOTE]
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Setting gain on amp with multimeter
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