Author Topic: Understanding the Analog Input Accuracy Specifications  (Read 3357 times)

Offline oiltronic

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Understanding the Analog Input Accuracy Specifications
« on: October 22, 2012, 09:42:38 PM »
Two questions regarding the analog input accuracy specifications, in particular regarding the MC050-020, Digital/Analog inputs, 0-36V range.

1.  Page 8 of the PLUS+1 Controller Family Technical Information document, rev KA (Nov 2011), mentions that the Analog Input Offset "can be" 80 ADC counts out of 4096, or up to 105/703 mV (low/high range).  One can see this offset when an input is floating or connected to the negative/0V/ground power supply line, and it can be significantly different between controllers.  Is this offset additive to the input, or a detection threshold?  That is, if the offset causes a reading of 100 mV when the pin is connected to 0 V, will a 50 mV signal read as 150 mV or remain undetected as 100 mV?  Will a 250 mV input signal then read as 350 mV or 250 mV?

2.  Page 11 of the same document states the "Worst case error (high range)" as 614 mV.  What, exactly does this mean and when would one experience this high amount of error.  (In other words, how do I avoid such inaccuracy?)