Difference Between Sampling DC Current and Pure DC Current, Electrolysis Risk at Microamperes

Hello,

Can somebody please help answering these questions?

1. What is sampling dc current and how it is different than normal dc current?

2. Can micro amperes of pure dc current cause electrolysis in body if passed for long time say 2 hours by holding 1.5 v AA battery?
3. How can I convert pure dc to sampling dc for micro amperes?

Thanks
Sal

Hello Sal,

three very unorthodox questions...
1. Never heard about "sampling dc current". Usually sampling is a term used in Signal Processing and means to take samples out of a changing signal (voltage) using a Sample Hold device. So, sampling a pure dc current does not make sense. What you get would be none changeing samples of a none changing signal.

2. The biggest danger in holding a 1.5V Battery for 2 hours is to get a cramp in your fingers. I would not fear any other danger. For sure not electrolysis... (even then if you touch the contacts )) )

3. See point 1. Does not make sense, but you could use a Sample Hold Circuit...

Thanks. I am studying something unorthodox. Dc sampling term is used in this study.
http://www.cs.cmu.edu/~dst/E-Meter/freq_resp.html

I am studying this device -e-meter.

Let me know if you know what they mean by that.

....
When the e-meter probes are placed across a 5.6K resistor, the 'scope shows a pure DC sampling current. DC is not preferred, because DC will cause electrolysis, creating a mini "battery" to be formed at the skin/metal junction which can invalidate the measurement. When AC is used, this battery is reversed at every cycle, minimizing the effect.

Sal,

Looks like the article you are referring to is someone reverse engineering one of the choicer bits of pseudoscience to be found within the religion of Scientology.

DC-Sampling here means exactly what Ulf wrote in #1 above. They are using a DC pulse train to take discreet time measurements of some quantity measured between the probes of the "E-meter." This quantity appears to be resistance.

Since this device is meant to be used on skin DC signals would in fact lead to electrolysis, as the author points out. A DC source would tend to cause some polarization and potentially ionization in the oil, salt, and water our flesh is coated in. This separation of charges could lead to a DC voltage offset that might corrupt the signal. Pulsing the DC (for the intents and purposes of this conversation essentially making it AC) allows the polarization and ionization to collapse, causing the error causing voltages to disappear.

At least, that's what I took away from the site. Though, if you're doing any kind of formal study on this, I would reccomend finding other sites. This one looks and reads like a novice researcher who approached the topic with a lot of pre-formed notions of what he would find. He cited no sources, and his write up was vague. I'd take the info with a grain of salt here.

Thanks. This is helpful. I'll look in to other sites as well