Validation of ECG Measurement and Atrial Fibrillation Detection

Inclusion Criteria: * Willing and able to participate in the study procedures as described in the consent form * Able to communicate effectively with and follow instructions from the study staff * Subjects enrolled into No\_AFib\_Group must have no known medical history of AFib and in normal sinus rhythm at the time of screening. * Subjects enrolled into AFib\_Group must have a known diagnosis of persistent or permanent AFib and be in AFib at the time of screening. Exclusion Criteria: * Physical disability that precludes safe and adequate testing. * Mental impairment as determined by the Investigator. * Pregnant women at the time of the screening visit. * Subjects with any Medical History, Physical exam, vital sign or any other study procedure finding/assessment that in the opinion of the investigator could compromise subject safety during study participation or interfere with the study integrity and/or the accurate assessment of the study objectives. This includes patients with known untreated medical conditions that are considered clinically significant by the Investigator, such as but not limited to significant anemia, important electrolyte imbalance and untreated or uncontrolled thyroid disease. * Physical exam limitations include but not limited to open wound(s) on the wrist and forearm where the subject will be wearing the watch. * Any history of wrist surgery with scarring in the area of the sensor location on the wrist where the subject will be wearing the watch. * Vital signs measurement, medical history, or physical exam finding that makes the subject inappropriate for participation according to the Investigator. * Tattoos or moles in the area of the sensor location on the wrist where the subject will be wearing the watch. * Skin conditions on either wrist that would preclude subject from wearing watch on either wrist. Severe symptomatic(or active) overly dry/injured skin, skin disorders, or allergic skin reactions such as eczema, rosacea, impetigo,dermatomyositis or allergic contact dermatitis on wrist and locations where the electrodes will be placed (e.g. chest,forearms, stomach), as determined by the investigator. * Known allergy or significant sensitivity to medical adhesives, isopropyl alcohol, or ECG patch. * Clinically significant hand tremors as judged by the Investigator. * Subjects with implanted cardiac devices such as a Pacemaker or an automated Implantable Cardioverter-Defibrillator.