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Aducm360 diagnostic current

Question asked by johnnybravo on Jan 23, 2016
Latest reply on Jan 25, 2016 by ABuda

Hello,

 

I am having difficulties in doing a good bridge diagnostics. The indications in the UG does not match with the values obtained by AD conversion.

 

One of the scenario exemplified in table 15 page 27:

 

ADC changes by ΔV = +50 μA × R1. For example, ~100 mV for R1 = 2 kΩ.

 

 

The indication in the UG is missleading and wrong.

 

This is how I see the equation. Please correct me if I am wrong:

ΔV = V0 - V1

When no diag current enabled, and the bridge is in equilibrium, V0= V1 = Vdd/2


If we enable 50uA current source for ADC0, then V0 will become:


V0 = 50uA * R1 + (50uA + i1) * Rbridge;


i1 is the current in the higher left side of the bridge.


I have tested with 2.2 Kohm R1 and R2, and 2.2Kohm bridge. the delta is 165mV.


Can a UG errata be created to show exactly how this should be used?


Thank you!





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