# EMG Grove Detector Conversion to Volts/Internal Gain

Hello,
I am using the Grove EMG detector with Arduino Mega and Mega Grove shield. I would like to convert the sensor readings to volts, can someone possibly advise on this?
I tried doing *5/2^10, which accounts for the 5V 10-bit ADC but the values are too high; so I am assuming the sensor has an internal gain that should be accounted for?
Thank you

Im not an expert, but a 10 Bit ADC will max at 1024, so if you are on a 5v system, 5 volts will read 1024, if you are on a 3.3 volt system, 1024 is 3.3 volts so 3.3v on a 5v system should give somewhere around 676 if it is linear, maybe use the map function, but definatly need to test and calibrate

Hi there,
Well in General, it the bits per how many mv it equals.
A mathematical relationship conveniently shows how the number of bits an ADC handles determines
its specific theoretical resolution: An n-bit ADC has a resolution of one part in 2n. For example, a 12-bit
ADC has a resolution of one part in 4,096, where 212 = 4,096. Thus, a 12-bit ADC with a maximum
input of 10 VDC can resolve the measurement into 10 VDC/4096 = 0.00244 VDC = 2.44 mV. Similarly, for the same 0 to 10 VDC range, a 16-bit ADC resolution is 10/216 = 10/65,536 = 0.153 mV. The resolution is usually specified with respect to the full-range reading of the ADC, not with respect to the measured value at any particular instant if that makes sense
Use the 3.3v instead of 5 volts, same relationship. of course the more bits the smaller the resolution that can be obtained.
HTH
GL PJ

i thought that was what i said… lol are you getting paid by the word?

1 Like

Hi Josee_Mallah,

According to the schematic, the output appears to be about 1.5 V when the electrode is plugged into J1 and the three electrodes are connected to each other. If you are converting AD with 10 bits, this would be about 300. I suggest you check it and see if it works.
And when the electrodes are attached to the arm, if they are not attached properly, the output may stick to the maximum or minimum!.
What do you mean by too ひｇｈ? Could you be more specific?

5V 10-bit ADC but the values are too high;

What do you mean by too high? Could you be more specific?

EMG_MDetecter.zip (20.1 KB)

1 Like