Hi Simon and wizard69!
i have looked at the Skenar description, and the research the device is based on (very interesting, there is a lot to read!)
Thank you for the suggestion.
I have also found the SIS Electro based on ultra low intensity direct current (LIDC), this might also be of interest to you.
From the litterature i have found iontophoresis is a "transdermal delivery system as charged molecules of medication penetrate through the skin to underlying tissues via wired or wireless skin patches."
This would be interesting to see if a simple project like this one (and the measurement of skin resistance parameters) can influence transdermal delivery (and to test both electrodes placements, voltage, and µa)
As a project i want to try a LIDC circuit (from what i read a voltage divider with potentiometer, and calibration with a multimeter of the load should suffice as a test project) but as the skin resistance varies greatly a potentiometer would be more suitable.
A simple LIDC is a battery, linear potentiometer and analog µammeter, is that correct?
The issue i see is that fine adjustement is needed as Kim Christensen noted (as 4µa is the reference)
Let's say 9v with the linear multi turn potentiometer as voltage divider up to 0.9v, max reference for skin resistance 250k , 0.9v (3.6µa * 250k)
I don't know if the tolerance is similar in voltage divider as it is as variable resistor.
But if the tolerance is 20%, it's 1.2 (4µa * 300k) but in range with 0.8 (4µa * 200k)
These are three option for a "simple "LIDC":
Battery, Potentiometer, µammeter.
Battery, resistors.
Constant current circuit (LTC6656 and MAX40006 as example like the thread mentioned)
in application:
test various skin resistance placements and condition (dry, hydrated, stratum treatment) with a multimeter (i've looked at data with baseline and distance), place resistor with similar value as load to test the circuit, adjust µammeter with the potentiometer to match values before placing electrodes on skin (measure changes in skin resistance)
What i do not understand is the mention of Vout upper and lower (R1 - R2), is there a different potential at the output of a voltage divider circuit and the "loading" effect (possible need to buffer the output first?)
I thought that with a potentiometer as voltage divider, it's the value of R1+R2?
see:
https://electronics.stackexchange.com/questions/328212/voltage-divider-equation-with-load-on-outputHave a great day!