Hi Sparkfun Team,
this is a question to Sparkfun Support:
I am interested in you Product “SparkFun Single Lead Heart Rate Monitor - AD8232” which looks really interesting. I understand already that this is not for medical diagnosis and not to be connected to main power. However, reading several things on the internet regarding self-made ECG circuits (or other biopotential amplifiers) and as a cautious layman, I wonder if you could provide me with some information on the safety and intended usages from your side. I thought about a 9V battery with a voltage regulator for 3.3V as the power source and connect this to a Laptop oscilloscope (but using again only battery power for the laptop).
- I am also specifically puzzled about this post on the AnalogDevices forum which refers to this board:
https://ez.analog.com/amplifiers/f/q-a/ … itor-board
“… and getting advice from a safety expert when testing a live patient.” ==> I thought about using this on myself, is this not the intention of your product?
- They also speak about a 10 microA limit: "We recommend using isolation resistors between the device and the electrodes to limit the current to the patient to 10uA (we specify in our datasheet how to calculate the resistor value) "
I see that your resistor values for LA, RA, and RL are in accordance with the AD8232 sheet example design. For RL it is 360 kOhm which would yield 3.3V / 360 kOhm = 9.2 uA current. However, why are the LA and RA resistors half, i.e. 180 kOhm? This would yield 18.3 uA if for some reason the 3.3V was directly connected to the electrodes,would it not?..can you explain the choice of these values?
- Any other things to watch out when using the board? Do you think this is suitable for someone with almost no electronic knowledge but interest in electrophysiology?
Thank you!
Toby