Muscle Sensors V3 returning noise

mooreadam: Sorry, this is probably a dumb question but do you want me to test the vs pins with a multimeter or through arduino? I ran this sketch to test the voltage but not sure if thats what you meant...

I meant with a multimeter. You need to make sure both batteries have juice and are pretty close in voltage to one another.

mooreadam: But when put on the muscle sensors every turns to 0.

I'm a little unclear what you mean here. Do you mean when you put on the electrodes? Are you still not seeing a response when you flex?

I zoomed in on your picture and see a problem. You shouldn't use both GND terminals on the sensor board to tie the common connection of the batteries together as this creates a ground loop. This should be done external to the board (as per instruction manual).

dlloyd:
I zoomed in on your picture and see a problem. You shouldn’t use both GND terminals on the sensor board to tie the common connection of the batteries together as this creates a ground loop. This should be done external to the board (as per instruction manual).

Technically that shouldn’t matter.

Advancer: Technically that shouldn't matter.

Well, technically it really does matter. The sensor board doesn't have a ground plane and it is an analog board with default gain of 10,350. I wouldn't assume the pot is adjusted to default (it should be checked), otherwise its safe to assume the gain could be anything up to 20,700.

If the existing ground loop creates 100µV of noise (0.1mV), this would get amplified to 1.035V default to 2.07V max which would return noise levels at 212 to 424 (ADC value).

dlloyd: Well, technically it really does matter. The sensor board doesn't have a ground plane and it is an analog board with default gain of 10,350. I wouldn't assume the pot is adjusted to default (it should be checked), otherwise its safe to assume the gain could be anything up to 20,700.

If the existing ground loop creates 100µV of noise (0.1mV), this would get amplified to 1.035V default to 2.07V max which would return noise levels at 212 to 424 (ADC value).

Unless Adam moved the gain potentiometer, then the gain is at the default setting. Use a multimeter to check its value. It should be around 50 kOhm.

Hey,

Sorry about the late reply - got caught up trying to get things ready for a hand-in at uni. I finally got it working, turned out there were two things causing the errors:

  1. The batteries where returning different voltages(even though I brought them at the same time)

  2. Some of my connections weren't as stable as they could have been so I did some resoldering and made everything a bit more secure.

Fixing these two problems seems to have solved everything, now I just need to improve the code to get the desired results. Thanks to everyone for offering solutions.

Cheers

Adam.