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I have had bilateral shoulder pain and then both arms and hands pain for around 7 mounts, which got much worse when I started working from home, with my laptop. The ultrasound of shoulder muscles revealed tendonitis which means inflammation in tendons. Nothing helped my pain relived, not the physiotherapy, message therapy or even pain killers and voltaren gel. In recent days I accidentally discovered that when I am working with my laptop, and touch its body, it is giving my body a voltage of around 37-40 V (I measure it with a multimeter set on AC V, one pin connected to the ground connection and the other in my hand)Laptop have a two pronged plug and is not grounded. When I checked this with one of my friends, he is getting around only 5-6 volts the same way of measuring on his own, ungrounded laptop. I bought this laptop (Asus Zenbook UX431) about 8 mounts ago, so it can explain the onset of pain in my body as well. My doctor refused to accept this can be a reason for my problems, but I have strong feelings and reason that this can be behind my issues. I wonder if you can also measure the voltage induced in your body while touching your laptop's body and tell what you get? I need more evidence if his can be the source of my problems. I just need some of your measurements and numbers, Thanks so much!

Reza-sh
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    It's probably improper posture made worse by working from home without a properly set up workstation. A static shock is 5kV and higher, 10kV or even 15kV or 30kV. 40V is nothing. – DKNguyen Apr 02 '21 at 02:49
  • Thanks for your answer DKNguyen, I don't get a shock when I touch the laptop, so it is apparently not too high, but I suspect because I have been using it for a long time, and long hours, if it is much more than normal it may have caused some inflammations... By the way if you can also measure your body voltage when touching your laptop it may help to understand.. – Reza-sh Apr 02 '21 at 02:58
  • Please note that static electricity discharges in microseconds, so not enough time to make a damage! – Reza-sh Apr 02 '21 at 03:19
  • That's just the discharge. You could be walking around holding that charge all day. – DKNguyen Apr 02 '21 at 03:20
  • Does the power supply have a proper ground connection? If not you will get the short of voltages you mention due to y cap leakage in the OSU input noise filter. || Consider arthritis ,/ rheumatism or polymyalgia rheumatica (which I have) or .... – Russell McMahon Apr 02 '21 at 08:17
  • Does the laptop have a three pole grounded mains inlet with ground, or simply two pole ungrounded mains inlet? If it has a grounded inlet, it must be connected to grounded mains socket. However it is unlikely that this is the cause of your pain. – Justme Apr 02 '21 at 08:40
  • My charger has a two pronged, ungrounded plug. I did ground it by a third ground cable connecting to a USB port a few days ago and the body voltage went away. – Reza-sh Apr 02 '21 at 12:04
  • The type of pain has always been weird for me, as it is not dependent to my movements or position and absolutely not responding to the physiotherapy and pain killers, it is very random across my both shoulders and arm muscles, and not like spine issue pains where they radiate to the arms. I had rheumatism tested negative. That's why I feel my nerves are stimulated or damaged, maybe due to this voltage... – Reza-sh Apr 02 '21 at 12:15
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    Laptops are terrible for tendonitis since they encourage poor posture and straining as you keep your arms unnaturally close together. You should try to minimize your laptop usage as soon as possible. Get a real keyboard and monitor, take regular breaks. That will also stop exposure to leakage current, but that is unlikely to be the problem. Chronic tendon injury can be severe and lifelong. You want to avoid making the problem worse. – user1850479 Apr 02 '21 at 12:33
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    I think you are chasing a ghost. It is extremely unlikely that the voltages you see are causing the symptoms you report. As many have said, common ergonomic issues are almost certainly the cause of your pain. I have been there myself. – Elliot Alderson Apr 02 '21 at 13:00
  • I see, and I get the posture issue. Just I wished I could ask some of you guys to measure your body voltage while you are touching your laptop, if you have a multimeter at home. – Reza-sh Apr 02 '21 at 13:06
  • @Reza-sh Physiotherapy isn't going to do anything unless you fix the root case because as long as the root cause exists damage continues to be done. I've had tedonitis and shoulder pains myself and once it is there, it is always there no matter what position you are in. – DKNguyen Apr 02 '21 at 19:50
  • @DKNguyen, That's right, I've been trying to do everything about this tendonitis, including different exercises, anti-inflammatory drugs and physiotherapy...So how did you get rid of that? – Reza-sh Apr 02 '21 at 21:08
  • @Reza-sh I got a tented keyboard and vertical mouse. Then proper height chair and desk where the keyboard height was independent of the monitor height. Now that I'm better, chair and desk height are less important, but the keyboard and mouse still are. It took many months. – DKNguyen Apr 02 '21 at 21:15
  • Having your arms straight and extended is good for your wrists when facing your palms down (pronation) but bad for your shoulders, but having your elbows bent 90 degrees is good for your shoulders but bad for your wrists when palms are facing down. You don't want to pronate your wrists since it causes the two bones in your forearm to twist around each other along with the muscles (look at diagrams online). If you keep your elbow 90 degrres and rotate your wrist so the palm alternately faces inward and downward, you will know what that twisted forearm sensation feels like if you pay attention. – DKNguyen Apr 02 '21 at 21:15
  • I definitely get a keyboard these days if that helps. But believe me, I still think my pain type is weird to be even from tendonitis, the physiotherapist told me even your inflammation is not that bad to cause this pain in your forearms and hands. Then they suspected to the neck, neck exercises and treatments didn't even make a difference. That's why I guess as you mentioned the root cause of my pain is still there... The pain follows a sinusoidal pattern which is intense for 3-4 days and lower for a few other days, independent of my exercises and treatments... – Reza-sh Apr 02 '21 at 21:23

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The power supply has a certain amount of leakage current. The leakage is coupling through the isolation transformer.

That open-circuit floating voltage you’re seeing is typical and within safety limits for a consumer device. You probably also saw it drop to a low value (a couple of volts or so) when you touched the laptop. That should tell you how weak this current actually is.

The applicable safety standards limit this current to 3mA or so. In most cases this will be lower than that - 1 or 2 mA or so. You can measure that, too, using the mA AC scale on your meter.

That said, you could be sensitive to it. Try using your laptop only off battery and see if that makes a difference. If it doesn’t, it may very well be an ergonomic issue like your doc is probably thinking. If it is, you could try connecting your laptop to a ground.

hacktastical
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  • Thanks for your answer. By unplugging the laptop the voltage dramatically drops to less than a volt... – Reza-sh Apr 02 '21 at 03:01
  • I should also mention that just using the keyboard or trackpad doesn’t expose you to the chassis. So there isn’t a direct path to your body. It’s highly unlikely that you’re a path for the leakage at all. – hacktastical Apr 02 '21 at 03:20
  • I used to rest my wrist on the laptop body which is metallic when typing, so directly connected most of the times... – Reza-sh Apr 02 '21 at 03:33