Dummy issue - pleas help.

[Makrorager]

Shift of values after exceeding a treshold (digital maximum issue)

Hellou,

first of all, sorry for bothering you with this elementary issue, I am not a technician (just beginning to learn about biosignals), but I would really appreciate your helping with one (I hope simple or trivial) issue. I recorded a signal (skin conductance level - SCL, uS unit) with my device - 16 bit, range of the measured SCL is 1-20 uS.

In a recording software I changed digital upper range - "digital maximum" - from 1024 to 65536 (minimum = 0).



The issue is that when I record the signal and the signal reaches about the half of the physical maximum (the range the device can measure SCL = 1-20uS), from the recorded signal I see something like "inverted-across-zero" values, they have negative values but as it is from oscilatory parts obvious, when the signal is lower than the bound about 10,5 uS then it is above zero value, when it exceeds 10,5 uS it become inverted and the values are (deposited) under zero axis.

Can this "phenomenon" be caused due to my stupid change of digital maximum to 65536? Thank you for any help!
Sorry for bothering you with this elementary issue

M.

 

[BradtheRad]

The method of calculating with signed binary is different than with unsigned binary.

There can be problems if you mix signed and unsigned variables.

Also variables can be of different byte-lengths.

Calculations will be less error-prone if you declare all variables in the same format as the largest number your program will handle.