Subway and Train Pacemaker Problem

The subway and many electric trains give off magnetic interference that is off the charts. I noticed this recently when using my iPhone App for magnetic fields.

This has to be bad for those with pacemakers - yet I have not read a thing. I feel it though!

Any thoughts on this?

5 Comments

I wondered too.

by clockman1 - 2012-10-07 07:10:51

This is something I have wondered too. Do electric trams in the UK have any effect on PM's? I have just got my bus pass( whoopee) and am curious to see if trams will be OK to ride on.
Any thoughts anybody. Surely electricfrank will have some idea.
Thanks in advance.
clockman1

shielded

by Tracey_E - 2012-10-07 09:10:06

Newer pm's are very well shielded and not affected by most EMF sources unless we're right on top of it.

The pm has a little switch in it, a magnet pulls the switch closed and puts it in test mode with limited function, just like when they interrogate it. You have to be right on top of the magnet for this to happen, usually less than 6". If it happens, it's annoying but harmless. It's still pacing, but only at your minimum rate. As soon as you get away from the magnet, the switch opens again and it goes back to full function with no harm done.

SUBWAY - there could be significant problem

by 1977-Hodgkins - 2012-10-08 01:10:22

"My point here is that were there a significant problem to a LARGE number of us, it would be well recognized."

My point here is that there COULD be a significant problem that is yet to be recognized.

Even if you get to work tired - that is significant. This could be sapping energy from all of us and needs further looking into.

asfaf

by boxxed - 2012-10-08 06:10:02

Anything that could be done to the device would be temporary. I haven't heard anything of the a device being re-programmed or permanently damaged because of EMI.

Subways & magnetic fields

by donr - 2012-10-08 08:10:17

I just spent an hour surfing the subject in many forms of the question. Very interesting - & often esoteric!

Stray magnetic fields are a problem for the subway systems (Undergrounds, Metros, etc), themselves in ways we would never even visualize! Some of the effects are pretty significant - to the subways.

The laws of physics transcend international boundaries, so the generalities apply universally.

All sub-surface trains are electrically powered & use some pretty large electric currents - nearly all being DC (Like battery power is DC); some are starting to use AC (Like our house power). The power is distributed by very large cables to the "Third Rail" that transfers the power to the individual cars on the tracks. You are wandering around the platforms & riding in the cars in the vicinity of multi-thousands of volts & significant Amperages (a measure of current flow) that create some significant magnetic fields.

These fields are of no significance to our biological bodies - that takes a magnetic field far in excess of the strength of an MRI magnet & then the effects on us are barely noticeable. For our PM's it is a different colored horse.

Once you are safely ensconced in the car (either seated or standing, crammed in like Norwegian sardines in a can) the voltages are no greater than about 600 DC, w/ slowly changing magnetic fields that vary w/ the speed & acceleration of the vehicle.

The greatest stray magnetic fields should be encountered during start up from a dead stop & the weakest during cruising speed. That's because the current flowing through the drive motors under the trains is greatest at start up & drops to a low value (Relatively) at cruise. For those w/ an insatiable curiosity - every time you feel a "Jerk" in acceleration while starting up, the current through the motors has been changed to keep from burning out the wiring in them. In the "Old " days, the train driver controlled the acceleration and/or speed by turning a rotary switch. Nowadays, a computer does it for him & a lot more smoothly, to boot!

The mag fields vary so greatly throughout the system, it is hard to make any generalizations about effects on our PM's. In General, the stray fields cannot be significant to most of us & our PM's. Otherwise, there would be warning signs all over the place at the entrances. I have ridden the Atlanta, Georgia & Washington, DC systems on many occasions w/o any noticeable effect on my PM. There must be thousands of PM hosts who ride the various underground systems world wide daily in their commutes to & from work. My point here is that were there a significant problem to a LARGE number of us, it would be well recognized.

For the OP (original poster) I'd like to ask if he/she has noticed any particular location for the app detecting larger or smaller fields. F'rinstance - in the center of a long car, does the mag field drop to a minimum, as opposed to right over the car's wheels ("Trucks" in the technical terminology of trains) where the traction motors are located?

In the FWIW Dept, according to one source I found, it takes about 1-7 Gauss of magnetic field strength to affect a PM. For stray fields, that's a pretty big number, since the fields fall off VERY rapidly w/ distance from their source. It takes 10 Gauss to erase the data on the mag strip on a credit card as another benchmark. For another benchmark we see daily, a Fridge door magnet holding up the latest coloring book page given to Grandma is about 10 Gauss. So - don't slap your fridge door magnets up against your PM.

And - last, but not least - it is safe to enter the underground railway systems. If it is not, your PM will tell you & you can leave quickly w/o serious harm - only discomfort.

As one last caveat - let me throw in this tidbit. I have exchanged Pvt Msgs w/ another member who was apparently having problems w/ an ordinary home dehumidifier. Whereas I have worked w/in very close proximity to one that was operating w/o any effect at all, she was affected by it at a very long distance (relatively) measured in several feet. Face it - we are all different i this regard!

Don

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