4 ms·

Hi, I'm glad to hear that, I'll be happy to help if you plan to build one! As for the idealized conditions, if I gently pass my finger on my laptop's aluminum

by xchip 13y ago

Hi, I'm glad to hear that, I'll be happy to help if you plan to build one! As for the idealized conditions, if I gently pass my finger on my laptop's aluminum case I can feel the 50hz hum, so that is why I have to unplug it to get that signal, it may be a laptop's issue. I will check with a desktop and post my results.

tonyarkles 13y ago
That sounds a lot like your laptop's chassis might be hot instead of grounded. Possibly an issue with the wiring in your house?
kryten 13y ago
50hz is pretty easy to knock our with a simple RC low pass filter. That should make a difference but it will probably attenuate the signal so you will need an instrumentation amp. 2 hours later... Ahh commercial grade design and massive BOM. Great work at keeping it simple :)
- xchip 13y ago
  Thanks! I am using an instrumentation amp indeed. As for the 50hz, I think I'm getting that noise just because my laptop is not grounded properly, no biggie
  - kryten 13y ago
    Probably right. Be careful! I had a Chinese clone Lenovo charger a while ago. There was 50v floating AC on the chassis when supposedly open circuit (!). Zapped myself on any metal part I touched. Fake one was dismantled for study and appeared to be missing most of the components. Tracing the circuit found a 1k resistor between live/hot and the ring on the PSU connector (laptop chassis DC ground). Turns out I was basically turning it into a voltage divider by touching it and was a the mercy of my quite high skin resistance :) Replaced with a genuine Lenovo one immediately resulting in no random minor electrocutions!
goblin89 13y ago
(So that's where that hum comes from. Been wondering for a long time.)
JshWright 13y ago
Which lead was the picture from? That biphasic morphology of the T wave is a little unusual. Do you have an older ECG to compare it to?
- xchip 13y ago
  Yes i noticed that too, I thought it could be because I put the leads where ever I felt like. I am using 3 electrodes, the reference one (ground), was on my right thigh, the other two were, one where my right chest meets the shoulder and the other one on my left side at the level where the floating ribs are... I placed them in non standard positions so that is why i may be getting funny values... But I agree that lower lobe is not in any ECG I have checked so far... I may go to the doctor to double check..
  - JshWright 13y ago
    That's close enough to the standard Lead II. A biphasic T wave in that lead is technically abnormal, but there are a number of benign causes. Certainly wouldn't hurt to check in with your doctor though (and you get to tell him a cool story of how you discovered it)
    - xchip 13y ago
      Hey! Thanks for letting me know! I'll try to get a real ECG as soon as I can... I hope that negative lobe is just an artifact :) Thanks again, and if you need help building one please let me know I'll be happy to help!

by xchip 13y ago

tonyarkles 13y ago

That sounds a lot like your laptop's chassis might be hot instead of grounded. Possibly an issue with the wiring in your house?

kryten 13y ago

50hz is pretty easy to knock our with a simple RC low pass filter. That should make a difference but it will probably attenuate the signal so you will need an instrumentation amp. 2 hours later... Ahh commercial grade design and massive BOM. Great work at keeping it simple :)

xchip 13y ago
Thanks! I am using an instrumentation amp indeed. As for the 50hz, I think I'm getting that noise just because my laptop is not grounded properly, no biggie
- kryten 13y ago
  Probably right. Be careful! I had a Chinese clone Lenovo charger a while ago. There was 50v floating AC on the chassis when supposedly open circuit (!). Zapped myself on any metal part I touched. Fake one was dismantled for study and appeared to be missing most of the components. Tracing the circuit found a 1k resistor between live/hot and the ring on the PSU connector (laptop chassis DC ground). Turns out I was basically turning it into a voltage divider by touching it and was a the mercy of my quite high skin resistance :) Replaced with a genuine Lenovo one immediately resulting in no random minor electrocutions!

goblin89 13y ago

(So that's where that hum comes from. Been wondering for a long time.)

JshWright 13y ago

Which lead was the picture from? That biphasic morphology of the T wave is a little unusual. Do you have an older ECG to compare it to?

xchip 13y ago
Yes i noticed that too, I thought it could be because I put the leads where ever I felt like. I am using 3 electrodes, the reference one (ground), was on my right thigh, the other two were, one where my right chest meets the shoulder and the other one on my left side at the level where the floating ribs are... I placed them in non standard positions so that is why i may be getting funny values... But I agree that lower lobe is not in any ECG I have checked so far... I may go to the doctor to double check..
- JshWright 13y ago
  That's close enough to the standard Lead II. A biphasic T wave in that lead is technically abnormal, but there are a number of benign causes. Certainly wouldn't hurt to check in with your doctor though (and you get to tell him a cool story of how you discovered it)
  - xchip 13y ago
    Hey! Thanks for letting me know! I'll try to get a real ECG as soon as I can... I hope that negative lobe is just an artifact :) Thanks again, and if you need help building one please let me know I'll be happy to help!