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Technical sheet questions MCC172



I have a 3 questions about the MCC172 card.

1.  In the datasheet of our MCC172 acquisition cards, there is an offset error value of ± 5.1mV. Does this value limit our accuracy to ±5.1mV or do we consider that the data can only be offset by a maximum of 5.1 mV and that in the post-analysis we can simply recenter to 0 mV.

2. Why is the dynamic range 100 dB? We have a 24-bit ADC and I find 144 dB as dynamic range.

3. Does the dynamic range means that the voltage input can varie between 33uV (noise flood) and 3.3 V (100 dB = 10^5, 10^5 * 33uv = 3.3 V ) if we want correct measurement? 

Thank you, 

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1. Your assumption is mostly correct. The offset is listed as a maximum not absolute and your offset may be less. You could measure it ahead of time then subtract the measured value from the data. To measure it, turn off IEPE source current and short the input. My 172 is, in a 22 Deg C environment, measured 200uVrms (approximately 1.2mV). 

2. There no such thing as a perfect DAQ board, so 144 dB is out of reach. The A/D itself isn't perfect plus there are amplifiers, filters and source current electronics that add error. As result, it is more like a very good 16-bit converter.  

3. The input measurement range is +/- 5 volts. You could test the inputs by turning off IEPE source current and applying a good quality 5 volt sine wave. Dynamic range is a signal to noise specification. Use it when comparing the 172 to other dynamic signal analyzers. 

best regards, 

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