We are reminded everyday of static electricity.
When we go shopping many times the action of rolling the cart across
the floor generates high potentials. Then we get zapped as we reach
for the can of peas. Most stores do little or nothing to make this
problem better. Some of the larger discount stores are the worse offenders.
Well, one grocery store chain has finally taken
a stand on getting the static potentials reduced. Food Lion has begun
to put drag wires on the carts.
The floors are not static dissipative but they
are on grade level and over concrete. The use of wires instead of
chains was a good idea. Even though the floors have little surface
conductivity, the pointed wire helps connect to what conductivity
is there but more importantly the wire can corona ionize the cart
to the concrete with very good effects.
This author performed a very unscientific experiment
at the Food Lion. One has to be careful not to look suspicious walking
through a grocery store these days.
I walked briskly around the store with a cart which
had not wire attached. The humidity was approximately 20% RH at 70
degrees F during my walk. I achieved almost 8 kV on myself holding
the cart.
When using a cart with the wire, I could not get
above 3 kV and it drained fairly quickly. Looks like it works.
Remember that a person can not feel a static shock
of less than about 3 kV. This means that the wire would keep the shocks
below most people's threshold of perception.
Of course on another day, the numbers could be higher
for the ungrounded cart but I suspect not for the cart with the wire.
This not only will make shopping there more comfortable,
it will help keep the checkout computer system from crashing as well
as the point of sale credit card systems from glitching. Not to mention
the destruction of the smarts in "Smart Cards."
