AnsweredAssumed Answered

Outliers at ends of measurement range

Question asked by gimbal on Apr 8, 2017
Latest reply on Apr 9, 2017 by NeoXu

I'm having some issues with the results I'm getting when performing AFE measurements over a large range of frequencies. I'm attempting to make 7 measurements (Channels 1-7 with 8 as the common reference for each) for a frequency range of 100Hz to 60kHz. I've noticed two things:

 

1.  Low frequency measurements seem to be inconsistent. This is a 4.7kOhm resistor between CH4 and CH8

 

2. I'm getting odd results at both the bottom and top end of the range for my RC circuits. Here is the plot of a 4.7kOhm || 0.1uF circuit between CH7 and CH8. Below about 500Hz, the impedance is somehow higher than the resistor, and above 40kHz we start seeing it spike again.

 

 

I'm using the 2-wire sample as a basis and have edited the sequence using the tool, and I see similar but not as exaggerated results with the EKSP tool. ( 4.7kOhm || 0.1uF )

 

Any thoughts on what could be causing this? The connection is via the 0.1" headers with soldered through-hole 

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