Hi guys, I'm working on my project with accelerometer. I know that accelerometer measure specific force or proper acceleration in general by deflection of proof mass. Proper acceleration is relative to free fall which could be analogy that proper acceleration is the relative acceleration between accelerometer(A) and a free fall object (B) . + Case 1: When accelerometer is on a table, it output 1G in Z direction. proper acceleration Z = m[ F(external) + F(gravity A) - F (gravity B) ] = 1G => what is external force that make accelerometer output 1G, is it normal force from the table ? + Case 2: When accelerate in +X direction , the proof mass is deflected by fictitious force. proper acceleration X = m[ F - F(gravity B) which I think is wrong. The fictitious force make the proof mass deflect in -X direction, how could it output positive value? Many thanks !!!