Well, everyone seems to be working hard. Me? I’m laying down
safety procedures. I’ve got a gas line spur that I need to get rid of.
It was put in for an eventual change from the electric water heater to a gas
heated system. Well, that ain’t happening anytime soon, as we just
replaced the water heater in the great flood of 2002. Basically, some
valve broke on the water heater unit and I woke up to 6" of water in the lab @
6:00am one fine Friday morning. Something like this once happened at UCCS.
And like a fool, I waded into it to open the sealed doors so the water can flow
out to the drain. Who would build a basement without a drain?
Especially a drain by the water heater? Well, that’s not the kind of
planning one gets from a Hellblazer education.
paving the path with good intentions, Brent came over and we played around with
the Spellman HV supply. That supply is a 30 kV, 2 mA supply, but still
nothing to ignore when its plugged in. I hadn’t tested it since I got it
off of EBay, so I was itching for the chance. Brent brought over his 40 kV
probe he had gotten and we figured we would ramp it up and see if the supply
worked – always a useful thing to know. So I had an old Fluke DMM and I
had also gotten 22 100 M Ohm HV resistors also off of EBay ($15 – such a deal).
So after a few trips to the hardware store and our local radio shack for some
wire and some terminal bars, we rigged up a simple test load for the supply.
Always a darn good idea to have a test load for an HV supply…
So we connected one of the resistors and cranked up the supply to 15 kV,
which is the rated voltage for these resistors. It was fun. But not
half as fun as listening to the crackle of the setup. Brent had gotten the
HV probe from EBay I think, but it didn’t actually come with the tip. So
one of the hardware trips was coming up with a screw of the correct size to
replace the tip. Well, actually, the original intent was to use the screw
to pull out (Brent theorized) the connector so he could screw in the tip he had
ordered. He had the wrong tip, so nothing we could do – short of
destroying the probe – would allow that tip to work. <heh>
So we just
used the screw as the probe. The vast pointy area of the screw threads
make a wonderful corona producing surface, but what the heck. At 25 kV we
couldn’t see any corona even in the dark – heck it was only half a mA max
anyway. Hardly anything to write home about. But we managed to crank
up the supply to most of its rated values. To the right is a picture of
the load we came up with. Nothing exciting to those seasoned veterans of
high voltage experimentation, but we were pleased any way.
I was especially pleased that Brent didn’t seriously injure himself.
Mind you, Brent is no dummy when it comes to electricity. He works with it
a lot, and is quite the safe guy. But in the first test, Brent went and
tried to put his hand near the one resistor to see if it was heating up.
Something that you’d feel perfectly safe doing at 50 volts and below. It’s
not like anything around this potential level going to arc out and bite you. After all, air is a pretty
decent insulator, and this is a DC voltage. Not some high frequency stuff
from some Tesla coil or something.
But 30 kV is a different thing entirely. It does jump out and bite you.
It was a very stupid thing to do. Brent has a lot of habits picked up
from his years of working with electricity. Some of the ones that are okay
for low voltages are really bad in the realm of high voltages. It’s just a
completely different world when you’re beyond the breakdown voltage of air.
You simply don’t have to physically come in contact with a conductor to get
We did observe something that we couldn’t adequately explain, however. If you look
at the picture above and to the right, you’ll see a green wire connecting the
two resistor bundles. When we got the voltage cranked up to 15 or 20 kV,
the green wire on the right of the terminal block started vibrating. At
first, when I mentioned this, Brent said that it was his hand shaking. I
couldn’t see any other vibration in the system, and I was looking intently.
So we shut everything down. Removed Brent from the system (i.e. no probe)
and tried the experiment again. The wire started vibrating again. So
now Brent was convinced that something unexpected was going on.
Note that this side of the resistive load was connected to the negative 30 kV
side of the supply. The system is symmetric, so the other green wire – on
the ground side – wasn’t vibrating at all. There was a metal bar under the
table. Brent thought it might have something to do with it. So we
moved the load away from it, and tried it again. Same result. Then
we turned off the lights to see if there was any corona that might help explain
it. No such luck – certainly to our eyes. And it’s pretty dark down
there with the lights turned off.
In any event, we think it’s just related to having a potential of 30 kV on
that wire. The air in the lab is pretty humidified, being so close to the
Pacific ocean. It’s not like it’s the national institute of standards down
there. Lousy grounds are still grounds, and we do have the ground return
to the supply in close proximity – so I wouldn’t be surprised if it was just
attracted to that. But we had never witnessed this effect, so it was kind
of cool to see. I’m sure it’s no mystery to HV veterans, so I’d love to
hear the real explanation – love to check my theories. Kinda cool to see.
Naturally, after we had
played around with the home made load, the real HV
test load I had snagged off of EBay for a steal showed up. The next
day. On the left you can see it in all it’s strange glory. The unit
stands about 18 inches high and is about 7 inches in diameter. The
resistors are the blue columns in the picture, and they are about 1.1 inches in
diameter. The top is aluminum, nicely curved structure – not a doughnut.
We don’t have a clue as to what potential its rated for, but the resistor
columns are 15 inches in height. So we’re guessing about 75 kV or so.
I think 30 kV, which is all I can output anyway, will be pretty safe. I
think, judging from the sheer size of the resistors, that the thing can handle a
kilowatt for short periods. I mean, the resistors are just simply massive.
In any event, I think I can use it to test the Bertan when the cable comes
sometime in the next week or two.
Oh, on Monday, the 90 kV supply showed up. Well, that was fun. It
was shipped in two packages. One contained the power control and supply
and the other the voltage multiplier. The package containing the
multiplier was soaked in oil – obviously insulation oil from the multiplier.
Hmmm. What to do? The poor UPS guys give me a choice. Accept
the shipment, or decline. Well, not knowing if this insulation oil was
hazardous, I said "decline, please", and they drove off with the packages.
The control system and main supply package was also soaked in oil, from the
runoff of the multiplier. I just wasn’t prepared to store something that
may have PCBs in it downstairs…
I once had several 7 kilo Joule capacitors (yow!) that were in my garage for several
years. They had PCB insulation, and I eventually had to get rid of them at
a toxic waste facility in the county. Not fun. Kinda terrifying to
have around. Not immediately dangerous, but something always gnawing at
the back of your mind. So I wasn’t in any mood to deal with this.
I’m still talking with the guys who sold it to me. It was insured, so the
money will all work out in the end. But I have to wonder. First,
what in the heck is UPS doing to these packages? I mean, I’m
assuming the people who sold me this supply shipped it in good faith. I
severely doubt it was leaking when they packed it. This is a company which
seems to be on the ball, and they would be just completely insane to do
something like that. So I believe it was in good shape and pretty well
But it was in a card board box, weighing in at 174 pounds. So that
wasn’t probably the best packaging scheme. Especially with fluids.
Got to have a hard container because people who ship things are pretty rough on
stuff… Likely they were moving it and BAM! It falls on the edge,
or something falls on it, or its dropped 4 feet off the back of some truck, or
falls off a conveyor belt. It likely bursts a seal or something, and then
the inevitable leak starts. God only knows how this will work out.
Definitely entertainment, though…
So I got some DB 15 connectors and some shielded 25 wire cable. I just
have to make up a connector, wire it to the lab jack, and I should have a
controller for the Bertan supply. The Spellman seems to have some remote
controls and monitors, so I should be able to drive that as well. But I
don’t have the schematic or pin outs yet from that unit… But they should
be here soon. But I’m getting the hang of LabVIEW’s programming language
and should have something measurable from the LabJack on the voltmeter and be
able to measure a supply input from a test input. That’ll be fun.
Automation is always cool. Then I’ll have to see if I can drive the
hydrogen mass flow controller. I’ve got the pin outs and signals needed
for those, and they look really straight forward. No big mystery there.
So that’ll be fun, too.
Since Brent is out of work, he’s volunteered to do some leg work for various
things that need planning and pre-positioning. That’s useful.
Hopefully he’ll lose his temporary unemployment, and he won’t have this
wonderful stretch of free time that he’s enjoying now. But until then, he
is going to be doing some useful stuff on various fronts.
In any event, I know it’s not much to report, but it was the best I could eek
out this weekend. Nothing too exciting, but fun none-the-less.