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Community Moderator Alumni are previous members of the Moderation Team, which ensures conversations are friendly, factual, and on-topic. Moderators are here to answer questions, escalate bugs, and make sure your voice is heard by the larger Fitbit team. Learn more
Hope you are doing great and enjoying some healthy activities @Armanmajidiii. Thanks for jumping in @supersmart01234
Our PurePulse heart rate tracking is the only heart rate technology to offer automatic, continuous wrist based tracking for all-day health insights and workout intensity. It is uniquely designed to measure heart rate all day, with always-on optical heart rate sensors that still maintain extended battery life also. PurePulse allows you to accurately track workout intensity and calorie burn with finely tuned algorithms that provide insight through interactive charts and graphs.
You can read some tips to improve accuracy since occasionally your tracker may have difficulty getting a strong signal. If you don't see your heart rate on your tracker, first make sure you are wearing it correctly. Experiment with placing the tracker higher on your wrist; because blood flow in your arm increases the farther up you go, moving the tracker up a couple inches can be helpful. Also, make sure you're not wearing your tracker too tightly; a tight band restricts blood flow, potentially affecting the heart rate signal. 
Though we've found that PurePulse provides better overall heart rate tracking than cardio machines or chest straps since it tracks your heart rate day and night, wrist placement during certain vigorous exercise is important but chest straps might be more accurate for this type of exercises as they are wore near to the heart. After a short wait, you should see your correct heart rate showing off. If this reading persists, try changing your Heart Rate setting from "Auto," which means the heart rate tracker is usually active when you're moving, to "On," which means the heart rate tracker is always active.
Hope this helps, I'll be around! 
Best Answer
Community Moderator Alumni are previous members of the Moderation Team, which ensures conversations are friendly, factual, and on-topic. Moderators are here to answer questions, escalate bugs, and make sure your voice is heard by the larger Fitbit team. Learn more
Hope you are doing great and enjoying some healthy activities @Armanmajidiii. Thanks for jumping in @supersmart01234
Our PurePulse heart rate tracking is the only heart rate technology to offer automatic, continuous wrist based tracking for all-day health insights and workout intensity. It is uniquely designed to measure heart rate all day, with always-on optical heart rate sensors that still maintain extended battery life also. PurePulse allows you to accurately track workout intensity and calorie burn with finely tuned algorithms that provide insight through interactive charts and graphs.
You can read some tips to improve accuracy since occasionally your tracker may have difficulty getting a strong signal. If you don't see your heart rate on your tracker, first make sure you are wearing it correctly. Experiment with placing the tracker higher on your wrist; because blood flow in your arm increases the farther up you go, moving the tracker up a couple inches can be helpful. Also, make sure you're not wearing your tracker too tightly; a tight band restricts blood flow, potentially affecting the heart rate signal.
Though we've found that PurePulse provides better overall heart rate tracking than cardio machines or chest straps since it tracks your heart rate day and night, wrist placement during certain vigorous exercise is important but chest straps might be more accurate for this type of exercises as they are wore near to the heart. After a short wait, you should see your correct heart rate showing off. If this reading persists, try changing your Heart Rate setting from "Auto," which means the heart rate tracker is usually active when you're moving, to "On," which means the heart rate tracker is always active.
Hope this helps, I'll be around!
Best Answer