Below is a link to an article from EMS1 regarding some tips on blood pressure readings, utilizing the appropriate equipment, etc. The most common error when using indirect blood pressure monitoring equipment is using an incorrectly sized BP cuff

https://www.ems1.com/ems-products/medical-monitoring/articles/5-errors-that-are-giving-you-incorrect-blood-pressure-readings-zJNOHnFJZOocufoS/