After reading this question, I simulated the tester as in the below circuit along with the current passing through human body:

enter image description here

Even I set the R_tester to zero, the current still will be around 10μA which is too small for a neon bulb. This is due to the Xc being huge because of tiny human body capacitance.

The only way the current to become 0.5mA is to increase the capacitance to around at least 5nF.

But the references say that the human body capacitance is around 100pF in series with 1.5k resistor.

According to these assumptions it seems something is not quite true here.

What could be the problem with the model I've drawn above?enter image description here

  • \$\begingroup\$ You have a paralell branch to your R_body and C_body with just an R in the 1-100 kohm range, depending on person, humidity and so on, or simplify it to your R_body bein in paralell to C_body, it will get you close enough. \$\endgroup\$
    – winny
    Commented Jun 21, 2017 at 13:09
  • \$\begingroup\$ But it is modeled in series not in parallel: rfwireless-world.com/Articles/ESD-basics-and-ESD-tester.html What is parallel to what you meant? \$\endgroup\$
    – user16307
    Commented Jun 21, 2017 at 13:16
  • \$\begingroup\$ Ah! For high frequency you are more interested in the series capacitance. For 50/60 Hz, you are mostly interested in the resistance. See en.wikipedia.org/wiki/Human-body_model. 1k5 in parallel with 100 pF as a first order approximation. \$\endgroup\$
    – winny
    Commented Jun 21, 2017 at 13:39
  • \$\begingroup\$ see my edit. Should that be modelled this way? that makes sense if the human body model is RC parallel circuit instead of series. \$\endgroup\$
    – user16307
    Commented Jun 21, 2017 at 14:10
  • \$\begingroup\$ I believe the problem is that the reference you are using is in error. If the body was modeled as a capacitor in series with a resistor, then no DC current could flow and DC sources would not be a hazard. We know this is not true. It makes much more sense for the body to be modeled as a resistor in parallel with a capacitor and then your issues would disappear. \$\endgroup\$
    – Barry
    Commented Jun 23, 2017 at 1:27

1 Answer 1


At a frequency of 50/60 Hz, the body capacitance is essentially an "open," so ignore it. that leaves the 500k in series with the 1.5k body resistance.
Since the 500K is much larger than 1.5K, you can also temporarily ignore it, so you are left with the voltage source (250V) in series with the 500k, making it a current source of (250V/500K =) 0.5ma. This current, into the 1.5K body resistance develops (.5ma x 1.5K =) 0.75V max (with feet grounded).

Your model should be as you have it, except the resistor needs to be grounded and the capacitor removed (or in parallel with the body resistor).


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