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How to use VoltDiff(): What is 'SettlingTime' and 'Integration'?

Minh T. Jul 8, 2019 08:05 AM

Hi. I'm trying to understand how how to use this function, what it measures (i.e., what the function returns when I feed it various types of sinusoidal signals of different frequencies) but the description of several parameters are quite confusing.

Since there are no readily available tutorials for how to make an analog differential voltage reading, I was wondering if someone could help met set up a simple circuit to show how 'RevDiff', 'SettlingTime', 'Integration' affects the function's return value. Here are a few questions I'm interested in: 

Q. What does integrating the input signal over the various available periods (250 us, 16.7 ms, 20 ms) mean? Would it return the RMS voltage of a sinusoidal signal over that period?

Q. What is the reason for incorporating a 'SettlingTime'?

JDavis Jul 9, 2019 09:04 AM

Settling time has a big impact on measurements that use an excitation voltage, because it affects how long the excitation is applied before the measurement. For simple voltage measurements like VoltDiff and VoltSE, settling time just needs to be large enough to charge a small amount of internal capacitance. On some dataloggers, settling time will also change the spacing of measurements when using repetitions. For VoltDiff, you can usually leave settling time at 0 to use the default.

Integration time has a major affect on your measurement. It is a noise filter. You won't get the RMS of the voltage, rather the result is the average of the voltage over the integration time. It removes the RMS voltage. This is desireable to remove the noise imposed on top of the actual signal from the sensor. The normal recommendation is to use a settling time to coincide with the local frequency of AC power, because it is a major noise source.

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