I would like a more dramatic label : Warning! You are in Danger! If I saw
that I would look around, take a few steps back and go to a safer place.
Reminds me when I made some tests in a steel net cage with a 50,000 Volt
transformer. Only label was a little sign on the door : Lock the door after
you!
Another peculiar memory. A engineer had built plexi box for testing TWTs. He
had built in security switches so that the high voltage be broken if someone
opened the door. One day, we found him on the floor, plexi box door open and
security switches taped over. He survived.
But high voltage can be fun too. When young, I had very thick rubber shoes.
Put finger on 100 Meg resistor connected to red terminal, and charged myself
to 20 kV (don't do that with a supply that can generate more than 10 mA !)
and walked out in the corridor. Saw some of the others and used index
finger, pointed close to the guy's nose and said 'you got something there,
have you cut yourself? ' . Well, in one such case of practical joke, I had
to run. My victim had a short fuse.
And the revenge was not far off. One day, I sat down as usual at my lab
bench, rolled the chair closer to the bench and ...SPRZZZT!... 20 kV
directly into my leg. They had used a high voltage cable from the other
room, connected it to the bench steel frame (standing on nylon feet) and
..you understand what of course.
From fun to reality. It's necessary to respect the laws and use safety
arrangements. Too many people die every year from current (not voltage). And
many are electricians and other technical guys. To be in the game is not the
same as being safe. Far from. We who use electrical equipments daily are
presumptive victims more often than we think. I will end this little extra
with a advice from my days working with dangerous boxes : one hand on
screwdriver, the other in the pocket....means: keep and eye on your left
hand when your right hand is in a working equipment. Has saved many lives.
Inge
----- Original Message -----
From: "Phil Nutting" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, July 08, 2009 9:49 PM
Subject: Re: [TN] IPC High Voltage PCB Marking and Spacing
Toby,
We use the creepage and clearance requirements as outlined in EN60601,
EN601, IEC950, etc.
For marking I use the European triangle with the lightning bolt/arrow.
If wording is used I use the requirements of ANSI Z535.6 to determine the
level of hazard presented by the high voltage;
Is death or serious injury a credible possibility? If No, then use CAUTION
If hazardous situation occurs, how likely is accident? If Possible, then
use WARNING
If accident occurs, how likely is death or serious injury? If Possible,
then use WARNING
If accident occurs, how likely is death or serious injury? If Almost
Certain, then use DANGER
The use of Danger versus Warning is a bit subjective. Take into
consideration the voltage and current levels present in the hazard.
I hope this helps,
Phil Nutting
Design for Manufacturing Engineer
Kaiser Systems, Inc.
126 Sohier Road
Beverly, MA 01915
voice: 978-922-9300 x1310
fax: 978-922-8374
e-mail: [log in to unmask]
www.kaisersystems.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Toby Carrier
Sent: Wednesday, July 08, 2009 3:20 PM
To: [log in to unmask]
Subject: [TN] IPC High Voltage PCB Marking and Spacing
Hi All,
Does anyone know of an IPC standard that states a requirement of high
voltage spacing and marking? I know that UL requires spacing based on the
voltage, but not for sure about IPC. Thanks for the help.
Toby
Engineering Technician
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