Hi group,
I read a bit about TENS and similar electrical stimulator units (not violet wands) and I have seen it mentioned that these units go typically from 0 -50mA or even
80mA. One manufacturer's site mentions "0-80mA (10V)".This raises many questions: Is it a voltage source or a current source? It cannot be possible to get 80mA current flowing through a human with only
10V. I measured the DC resistance of myself and it varies between 10k and 200k, depending on conditions. For 80mA the unit would have to be able to deliver 800V into 10k resistance.Also, these units can deliver variable frequency, burst duration, variable strength (voltage or current?) and audio.
I connected my arm (wetted a little) to a DC bench supply as well and cranked the voltage up until I started feeling something. It needed 30V before I could even notice it. This would substantiate that the TENS unit needs to generate quite a high voltage to deliver the currents specified.
I find this all a little confusing an maybe someone has a circuit diagram for the output stage of such a unit so that I can understand this better? Do they use a stepup transformer with a switcher in the output amplifier stage perhaps? This would complicate things if a current source were used.
Perhaps someone knows where I can find out? I don't own such a unit but I am very curious - typical engineer...
As far as I could establich, there seems to be no detailed information available on the www about the actual driving circuitry in such a unit.
Regards Ben