1. Home
  2. Electronics Equipment
  3. How to perform 200kHz-5MHz sweep while maintaining 200mArms?

How to perform 200kHz-5MHz sweep while maintaining 200mArms?

I am performing a test to measure the impedance through electrode pads placed on opposite parts of the human body. The protocol requires that the measurement be made by maintaining an AC sine current of 200mArms, sweeping the frequencies from 200kHz to 5MHz, and measuring the Vrms between one electrode and a reference point on the body. The impedance is to be calculated by dividing this voltage by the known 200mArms current.

How do I sweep frequencies while maintaining a constant 200mArms current using a HP 33120A (waveform generator w/ 0-15MHz freq and

0-10V peak to peak) or a HP 4192A (impedance analyzer w/ 0-15MHz freq and -1V-+1V peak to peak)? Can I construct a circuit external to one of these units and accomplish the 200mArms sweep? If not, what lowest-cost set-up could?
Reply to
Michael
Loading thread data ...

See quasi-answer on sci.electronics.components. And, please learn to cross-post, rather than posting multiple times, so that your messages will be linked across the newsgroups. Thanks!

Reply to
Walter Harley

snipped-for-privacy@berkeley.edu (Michael) wrote in news: snipped-for-privacy@posting.google.com:

I don't think your generator(s) will output 200ma into a load. BTW,flatness of your generator probably depends on a 50 ohm load Z.

--
Jim Yanik
jyanik-at-kua.net
Reply to
Jim Yanik

Before you get too deep figuring out "how" you do this, have you determined "if" you may do this? I sure don't want anybody to put 200 milliamps through me! Assuming a typical body resistance of about 1500 Ohms, doesn't that imply about 60 Watts? True, I don't know what happens to body impedance as you get into the low HF range, but maybe you should review the literature on tissue heating one more time. Perhaps all your volunteers are already cadavers. Or maybe you Berkeley guys don't know milliamps from microamps.

Ed wb6wsn

Reply to
Ed Price

determined

through

on

oh I hope it is microamps.... I've heard that 30millamps can kill!

Reply to
Mark

Less than that can kill; but it has to actually get to the relevant muscles (heart, diaphragm).

In this case, the *intent* of the OP was to use frequencies of 200kHz and above. At those frequencies, the energy travels mainly on the surface of the conductor, that is, on the surface of the body. Apparently, there is not even any sensation of being shocked, even at fairly high currents.

If you do a bit of Googling for "high frequency current human body" (without the quotes) you can learn more about this.

The key point, though, is that word "intent". As we all know, what actually happens when you hit the switch on a piece of equipment is not always exactly what we intended to happen. There is altogether too much risk that an equipment fault or an operator error would result in substantial current being delivered at lower, lethal, frequencies.

Reply to
Walter Harley

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.