Brian, et al,
The IEC 60990 body model circuit is the traditional test circuit
that has been used by the IEC for more than 50 years. It combines the
inward & outward conducting skins into one lumped circuit model of RS = 1500
ohms paralleled by Cs = 0.22uF. It is usually described as a large area
contact model (salad plate sized contact). This model was developed long
before any of the work to further develop the requirements in all of the
detail shown in the voltage documents (60479-5 & 61201). Other models of
interest have been fingertip contact model and palm sized contact model.
You may remember that I gave a paper at PSES08 which reported on
using actual measurements to determine the Rs & Cs value. This paper
involved deconvoluting the X-Y ellipse generated by the application of ac
current to the body to retrieve the Rs & Cs. The purpose of the paper was
to demonstrate the method. As far as I know, no researchers have taken more
data & repeated the calculations to get statistical values for a number of
contact conditions.
Further, I have presented a number of PSES papers showing analysis
of situations based upon the standard circuits in IEC 60990. These analyses
provide the basis for confirming the provision of needed electric shock
protection in the situations evaluated.
There is plenty of room for getting additional, up-to-date data on
the human body to support further modeling of electric shock situations.
There is major interest among electric shock experts such as members of IEC
TC64/WG4; work in this area seems to be just getting underway.
All of this will be long term research work so don't expect results
tomorrow.
:>) br, Pete
Peter E Perkins, PE
Principal Product Safety Engineer
PO Box 23427
Tigard, ORe 97281-3427
503/452-1201 fone/fax
p.perk...@ieee.org
_ _ _ _ _
Pete,
Is this a 'typical' reactance, and a similar capacitance as used in the
IEC60990 networks?
Brian
From: Pete Perkins [mailto:00000061f3f32d0c-dmarc-requ...@ieee.org]
Sent: Friday, October 10, 2014 5:30 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Human fingertip capacitance.
Gary,
The modeling of the human body from an electrical point of
view has been going on for almost 100 years with major strides in
understanding in the '40s & 50's and major gains again in the '90s with the
advent of CAT/MRI scans providing overload detail in the body construction.
The developers of IEC 61201, 'touch voltage threshold values
for protection against electric shock', have used commonly accepted values
in developing their evaluation as presented within that standard.
Specifically, the capacitance of human skin used is in the
range of 0.01 uF/cm2 to 0.05 uF/cm2 with a median value of 0.03 uF/cm2.
Fingertip contact is in the range of a few cm2, from my experience.
Perhaps this is adequate info for you to move ahead in your
work.
:>) br, Pete
Peter E Perkins, PE
Principal Product Safety Engineer
PO Box 23427
Tigard, ORe 97281-3427
503/452-1201 fone/fax
p.perk...@ieee.org
_ _ _ _ _
Trying to set up a jig to test some capacitive touch-panels. It's an
automated probe that disturbs the capacitive field of the sensor - but I'm
clueless what kind of value to shoot for. I thought about the ESD gun
capacitance but I don't know if that actually matches a human fingertip - or
it's the whole body, or that the capacitance of the body of the ESD gun
itself is used to calibrate to some human figure tip capacitance.
I've got some research to do but does anybody have a starting point and a
reference for the capacitance of an average human fingertip. I have the EE
working the design to go back to the component supplier but haven't heard
back from them yet.
Thanks
Gary McInturff
Reliability/Compliance Engineer
Esterline Interface Technologies
Featuring
ADVANCED INPUT, GAMESMAN,
and LRE MEDICAL products
600 W. Wilbur Avenue
Coeur d'Alene, ID 83815-9496
Toll Free: 800-444-5923 X1XXX
Tel: (208) 635-8
Fax: (208) 635-8
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