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### Topic: EMG sensors, how do they work? (Read 4354 times)previous topic - next topic

#### Archelon

##### Jun 01, 2012, 12:12 am
Hello! Im a beginner in this whole arduino world and right now i've got my eyes on the so called EMG sensors. I have done some googling and found out that there is no "simple" kind of sensor that you can buy from arduino itself or sparkfun and so on. how comes?
How does this kind of sensors work and is there no kind of electrodes you can plug directly to the arduino without some kind of middle station or is that needed, like the component specified in this thread http://arduino.cc/forum/index.php/topic,65804.0.html?
Thanks so much in advance!
/A

#### oric_dan

#1
##### Jun 01, 2012, 12:38 am

If you read the link given, you'll see that EMG signals are only in the 20-30 mV
maximum range, so you need an amplifier to boost the signals into the range
that Arduino can use = 0-5V. So, figure an amp gain of 200 or so.

http://en.wikipedia.org/wiki/Electromyography

Also, you have to be careful when hooking up anything to the human body that
uses voltages, so professional amps have isolation circuitry and/or run off batteries,
etc, to preclude electrocuting the humans. Also, since the signals are so small, you
have to design the ckt to reject extraneous noise sources, like 60-hz mains, etc.
Also, the electrode contact potentials with the skin drift over time, so you need to
take that into account too in the amp design. On and on. You can probably
google for EMG amp design.

#### robtillaart

#2
##### Jun 02, 2012, 05:52 pm
[just to discuss (disrupt) an alternative]
You can also use the - arduino.cc/it/Reference/AnalogReference - use the option INTERNAL and you have 1024 measurepoint on 1.100 V ==> about 1.1 mV per step.

For the 10 mV delta you have this means only 8 or 9 steps possible, and given at least 1 (or2) bit will be noise you effectively have 2 or 4 levels .

So the amplification proposed by oric_dan will give far better results.

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

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