Simon, there is "wrist detection" in Settings which is turned on by default. The back of the watch has LED lights which are used to track heart rate and I'm not sure if there are other sensors used when you do an EKG, but through these and probably also because of sensors like accelerometer, gyroscope and so on the watch knows if it is on a wrist or just sitting on a table and of course if it's charging it knows it can't be on the wrist unless you have a built-in Qi charger in your wrist. Here is an article which explains the heart rate monitoring:
How Apple Watch Measures Heart Rate & Its Accuracy Explained The Apple Watch is capable of tracking many health-related aspects of your body, including heart rate. The heart rate monitor is less accurate than you might think, but there are ways to improve the accuracy of heart rate readings received from the Apple Watch. The Apple Watch Series 5 was released in September 2019, and it remains one of the most sought after smartwatches available. Several smartwatches and fitness trackers on the market have the ability to track heart rate, but the Apple Watch remains one of the most commonly purchased products with heart rate tracking. It was cleared by the FDA for its precision. Despite that, studies have suggested that the Apple Watch's accuracy is less than 50-percent. The Apple Watch tracks heart rate using photoplethysmography. While this sounds complicated, it just means it uses light to track your heart rate. Red things, like blood, reflect red light and absorb green light. The Apple Watch uses green light to help detect how much light is being absorbed by the blood in the veins, and that fluctuation can be used to track heart rate. The green LED lights flash hundreds of times each second in order to get an accurate reading. This is the type of reading it takes as someone is actively working out, and it supports tracking heart rates that are 30–210 beats per minute. The heart rate sensor also uses infrared light to track heart rate in the background all the time, and to provide heart rate notifications. How To Increase The Accuracy Of Readings Heart rate can also be tracked using the Digital Crown on the side of the Apple Watch. When you place the finger of your opposite hand on the crown, it creates a closed circuit between your hands that goes through your heart. Because of this closed circuit, the heart rate measurement is much more accurate, and you will also get a much faster reading than what you experience with other methods. The Apple Watch’s accuracy level can be different from person to person. For some, it’s impossible to get a heart rate reading at all. However, there are things that can be done to help get a more accurate heart rate reading more consistently. Making sure the Apple Watch fits well is one of the best ways to ensure an accurate reading. The watch should be not too tight or too loose, and it needs to remain on the top of the wrist a all times. Wrist detection also needs to be turned on in order to have heart rate detection whatsoever. Anytime Power Saving mode is turned on, the heart rate sensor will also stop tracking the heart rate. Tattoos, skin perfusion, and the type of movement may also affect the accuracy of the Apple Watch readings. From: viphone@googlegroups.com <viphone@googlegroups.com> On Behalf Of Simon A Fogarty Sent: November 11, 2021 12:13 AM To: viphone@googlegroups.com Subject: RE: apple watch Yeah, I setup a passcode a week or so back for the mask unlock of the phone, And was interested to see that it locked when I took it off, I wondered how it knew, Other than it’s back isn’t against the skin anymore. I wondered if there might be something in the strap. From: viphone@googlegroups.com <viphone@googlegroups.com> On Behalf Of Sieghard Weitzel Sent: Thursday, 11 November 2021 8:18 pm To: viphone@googlegroups.com Subject: RE: apple watch Yes, the watch knows if you wear it or not. When you first put it on and if you set a passcode you have to enter that or you can set it to unlock when you unlock your iPhone, once that is done you don't have to enter a passcode as long as it stays on your wrist, but as soon as you take it off you have to unlock it again. Also, if you use Apple Pay on the watch and you have unlocked it before, then all you have to do is double press the side button (the flat one, not the digital crown) and your wallet coms up, you hold the watch up to the card terminal and it will authorize, no extra entry of the passcode is required. From: viphone@googlegroups.com<mailto:viphone@googlegroups.com> <viphone@googlegroups.com<mailto:viphone@googlegroups.com>> On Behalf Of Simon A Fogarty Sent: November 10, 2021 1:51 PM To: viphone@googlegroups.com<mailto:viphone@googlegroups.com> Subject: RE: apple watch Sieghard You’ve just mentioned something I’m always thinking to ask, If the watch isn’t on it wont ring, at least I don’t think it does, But if you put it on, It does, Or with anything relating to the watch, that Or is the back of the watch sensitive to the arm being securely attached. From: viphone@googlegroups.com<mailto:viphone@googlegroups.com> <viphone@googlegroups.com<mailto:viphone@googlegroups.com>> On Behalf Of Sieghard Weitzel Sent: Wednesday, 10 November 2021 8:11 pm To: viphone@googlegroups.com<mailto:viphone@googlegroups.com> Subject: RE: apple watch Hi Richard, You can also do this on the iPhone, but as I said in my reply to Doug who in a different thread recommended this feature I caution people about this feature because it will answer whether you want or not. In the case of the Apple Watch it may not do so if you are not wearing the watch, but if you enable this on your iPhone for example and don't actively hang up the other person may not hang up either and continue to listen or maybe your phone is not really close and you don't hear it ringing which could especially happen if you have it set to mute and then again the call will be answered and if you have a conversation going or maybe are in some other situation where you really don't want somebody to hear what is going on then you have no control over this. I have used this feature occasionally like for example if I was maybe expecting a call but I was doing something where my hands were dirty or occupied like cooking, woodworking or digging in my garden, but I really make sure I turn this off again right away when I don't need it any more. From: viphone@googlegroups.com<mailto:viphone@googlegroups.com> <viphone@googlegroups.com<mailto:viphone@googlegroups.com>> On Behalf Of Richard Turner Sent: November 9, 2021 7:55 AM To: viphone@googlegroups.com<mailto:viphone@googlegroups.com> Subject: RE: apple watch OK, this is the second time this week already I get to eat my words. I guess either things changed withWatchOS 8 or I was accidentally hitting the answer call button when I thought I was doing a two finger double tap. IN look through the settings, I did discover something else that is possible to set up. You can set the Apple Watch to answer automatically after a set number of seconds. ON the Apple Watch, check under Settings, Accessibility and flick to Auto Answer Calls. Turn it on by double tapping with one finger a couple of times as the first one opens the setting, then the next turns it on. Then, there is a scroll bar that probably defaults to 5% which when you flick once more says 3 seconds. Go back to that scroll bar and flick up I checked it out up to 50% which was about 30 seconds. Anyway, not something I will use unless I know my hands are going to be busy doing dishes or something, then it might be a good thing to set. Sorry for the misinformation. Richard “Reality is the leading cause of stress for those who are in touch with it.” – Jane Wagner My Web site: https://www.turner42.com From: viphone@googlegroups.com<mailto:viphone@googlegroups.com> <viphone@googlegroups.com<mailto:viphone@googlegroups.com>> On Behalf Of Janet Bell Sent: Tuesday, November 9, 2021 7:35 AM To: viphone@googlegroups.com<mailto:viphone@googlegroups.com> Subject: Re: apple watch sorry Richard a two finger double tapp does absolutely nothing. Janet On 09/11/2021 13:45, Richard Turner wrote: A two finger double tap will answer a call on the watch. Richard "Reality is the leading cause of stress for those who are in touch with it." -- Jane Wagner website: www.turner42.com<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.turner42.com%2F&data=04%7C01%7C%7C92b86f9dac1842a9aa3108d9a39681e3%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637720689088893310%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=8S5UeDKmUYTcbS%2FwY2nlr%2F9KPDYBAL1tJgkF0qA8FXI%3D&reserved=0> (Sent with my blue iPhone 13 Pro) On Nov 9, 2021, at 5:39 AM, Janet Bell <tagli...@gmail.com><mailto:tagli...@gmail.com> wrote: please could someone remind me how to answer a call on an se apple watch. Janet -- The following information is important for all members of the V iPhone list. If you have any questions or concerns about the running of this list, or if you feel that a member's post is inappropriate, please contact the owners or moderators directly rather than posting on the list itself. 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