There are published reports of scientific comparisons between automated and manual blood pressure measurements that show:
* lower readings from automated (https://pmc.ncbi.nlm.nih.gov/articles/PMC5515188/, https://pmc.ncbi.nlm.nih.gov/articles/PMC8031494/)
* no differences between them (https://www.academicmed.org/Uploads/Volume5Issue4/281.%20%5B1288.%20JAMP_Arpita%5D%201409-1411.pdf)
* higher readings from automated (https://pmc.ncbi.nlm.nih.gov/articles/PMC4843288/#sec9).

Manual measurements require equipment calibration and proper training of the operators. They are not fault-free.

I have been obtaining normal blood pressure readings weekly since 2021 using an automated instrument, which I share with my cardiologist.