This blog article talks about using an automation controller to keep a server room from getting too hot. Continue reading “Cooling a server room”
Cooling a server room
Shielded and yet not shielded
The implicit promise made by the maker of an RCA cable is that its center conductor is shielded by its outer conductor. I have, however, been astonished in recent times to see that many RCA cables are not shielded at all. Continue reading “Shielded and yet not shielded”
Welding current redux
It will be recalled (blog article) that I had recently started getting familiar with an inexpensive inverter welder. What became pretty clear early on is that the number in the display does not match the number of amperes of welding current delivered to the welding rod. Alert reader Dave posted a comment:
Can you accurately anticipate what amperage to expect given the readout on the machines as a ratio to the readings you have gotten on the ammeter? Perhaps this is an opportunity to do some more experimentation…
Prompted by alert reader Dave, I did some more measurements. Here are the results.
Measuring welding currents
(followup: I have now measured more welding currents — blog article)
It will be recalled (blog article) that I recently took a stick-welding course. I also recently purchased an inexpensive inverter-type welding machine (shown at right), and a neighbor of mine also purchased an inexpensive inverter-type welding machine.
Each welding machine has a rotary knob for picking the welding current. And each welding machine has a three-digit numerical display. The question that arose for my neighbor and me was, can we safely assume that the number in the display will be the number of amperes of actual welding current? The answer turned out to be “no”. Continue reading “Measuring welding currents”
Death capacitors
Readers of this blog are already aware that I enjoyed the movie Glass Onion (blog article), from writer/director Rian Johnson. At about the time that Glass Onion became available for streaming, it came out that Johnson had just gotten done creating, writing, and directing a ten-episode television series Poker Face (Wikipedia article). I have greatly enjoyed all five episodes of Poker Face that have aired thus far.
Which brings us to episode four of Poker Face, entitled Rest in Metal. This episode has a plot element called a “Death Capacitor”. Which is what I will now discuss. Continue reading “Death capacitors”
Choosing a LAN type
The executive summary for this blog article is that ethernet is faster than 5-gigahertz wifi, and 5-gigahertz wifi is faster than 2.4-gigahertz wifi. (I imagine that most readers of this blog already expected this to be the case.) Continue reading “Choosing a LAN type”
Publishing things on SSRN!
It turns out that anybody who wants to, can publish things on SSRN (Wikipedia article). SSRN, it will be recalled, is an initialism for Social Science Research Network (web site). To test this out, I created an account at SSRN and uploaded The Fool’s Errand that is DOCX. You can see it here: https://ssrn.com/abstract=4346907. This blog article describes the process and the results. Continue reading “Publishing things on SSRN!”
Paint first or glue first?
Folks, the subject line says it all. When I am assembling a plastic model kit, should I glue the parts together, and then paint the parts? Or (as the instructions seem to suggest) should I paint the parts first, and then glue them together? Continue reading “Paint first or glue first?”
How clamp-on DC ammeters work
I imagine many readers of this blog have some idea how a clamp-on AC ammeter works. You have some wire with AC current in it, and you open the jaws of a clamp-on meter and you close them around the wire. The alternating current makes a constantly changing magnetic field around the wire. It is a fairly realistic goal for the jaws to capture basically all of the lines of (constantly changing) magnetic flux surrounding the wire. If you have the luxury of being able to assume that the frequency is known (and depending on the continent where you are located, this may well be a safe assumption), you can proceed in a very straightforward way to design a simple and inexpensive and quite accurate AC ammeter. I have had this Micronta (Radio Shack) meter (seen at right) in my tool kit for some fifty years now, and it has served me very well.
But nowadays there are clamp-on DC ammeters. A wire carrying a DC current does not (by definition it does not!) generate any changing magnetic field! A traditional meter like the one described above has nothing to measure if it is clamped onto a wire containing a DC current. How can a clamp-on DC ammeter possibly measure a (perhaps constant) DC current? Continue reading “How clamp-on DC ammeters work”
Diatomic carbon
One of my pastimes is trying to guess which sound bites, if uttered at a cocktail party, might lead to the turning of heads and might lead to other party guests clustering around with great interest. (See past blog articles.) Here is another: diatomic carbon. Continue reading “Diatomic carbon”