There’s a good overview of these systems here:
The Synchronous Wire system is the most popular system in the United States. Clocks are run using a power circuit that acts as its time base. The clocks receive an hourly correction which synchronizes both the minute and the second hand. Every 12 hours the clock receives a daily correction to keep the clock perfectly synchronized.
When I first started working in the medical imaging field (circa 1989), we’d run into issues with these clocks, a lot. Hospitals and health-care facilities were big users of these (there’s a clock in every patient room, hallway, and procedure room), and one particular piece of equipment (a Phillips “Classic” generator) was particularly susceptible. The generator used a motor-driven, linear variable autotransformer (think Variac or Powerstat) to adjust for line voltage changes – and the signal injected onto the mains by the clock controller (typically around 3500 Hz) would mess with the voltage regulation circuit, and the motor would “hunt” for the duration of the pulse (usually 5 or 10 seconds), The generator would be disabled or locked out while the motor was moving, and this would drive the docs and techs crazy (since it happened hourly).
I’ve also come across a few old power quality threads discussing these clock pulses causing standby / hybrid UPS systems (notoriously sensitive to anything that might indicate the start of an actual outage) to switch to inverter improperly.
Back in the day, the old BMI-4800 power analyzer had a “high frequency noise” detector which looked at broad spectrum harmonics or noise, and output a distinctive “picket fence” 24 hour log when these clocks were present (I still miss this diagnostic / reporting feature on modern power analyzers). I’m sure I have an example of this graph kicking around somewhere but can’t put my paws on it at the moment. I suspect any graphs I recall pre-date digital images (when I would create reports with blank boxes, and manually paste in photo-copied disturance graphs) so I’m not finding anything in trip reports or old PowerPoint presentations)
Resolving these issues? Sometimes we’d consult with the facility engineer – oftentimes these were turned up to “10” (maximum) and we could get the amplitude turned down to the point where it worked but did not cause problems. Sometimes we’d get the clocks reprogrammed to only correct 2x a day (noon and midnight) when it would be unlikely to affect the equipment. Some resourceful field techs developed a filter circuit to protect the regulation circuity; although that was sometimes not permitted (FDA requirements for x-ray equipment forbids modification or retro-fitting).
I don’t hear too much about these lately. Clocks are now often digital, controlled wirelessly or via ethernet. Switched-mode power converters have replaced old analog systems.
Breaker Q1 in the WCS electronic box trips on a sporadic basis. The breaker is the M4 and M5 fan motor overcurrent protection. We have replaced the breaker multiple times.
First pass, we noticed three very high current swells in the ground current data:
We also saw 100s of very serious arcing voltage transients, not related to load current changes or other voltage events. The transients showed up on Phase-Neutral and Neutral-Ground, but the NG transients were much lower amplitude (secondary, not the primary issue).
Finally, we captured three current swell events that clearly show equipment faults to ground (notice the elevated ground current) immediately following voltage transients – cause and effect.
Figuring out the cause of the transients is an exercise for the local service engineers or an onsite power quality engineer. But we’ve got a pretty clear linkage here between transients and equipment faults. Most of the time, power quality problems are a lot less concrete and clear.]]>
Annoyance #1: Called the manufacturer to get a replacement cord (I had troubleshot it down the cord itself). Turns out the cord is hard-wired into the motor, so the solution is to replace the motor. (bad answer, the motor itself is fine). Why is a simple power cord that will invariably get a bit of wear and tear not be easily replaceable?
Annoyance #2: Yes, it’s under warranty, but it requires both a service call (to replace the motor) and shipping charges. Um, no.
Annoyance #3: Additionally troubleshot the cable and discovered the intermittent was in a little inline molded box containing an LED, the sole purpose of which (as far as I can see) is as a redundant and unnecessary troubleshooting tool – since both the chair control pendant and the transformer also have LEDs to indicate power on.
Solution: Cut the molded box LED out, strip and splice the cable (nicely soldered and insulated), it’s a wee bit kludgy with electrical tape, but perfectly safe and solid). Took about 15 minutes including time to heat up the soldering iron and then test the crap out of it afterwards.
Ultracomfort America – not impressed.]]>
I’m probably over-killing the set-up here – running the 2.5mm mono output of the recorder through adapters (2.3mm -> 3.5mm -> 1/4″), then through a DI to get XLR out, and into a Mackie mixer to tweak the sound a bit (cutting out some of the highs and lows, optimizing the level) and into the recorder. I’ve got a set of headphones to listen in now and then. Next time I’m out I’m going to pick up my spare monitor speakers at my storage locker so I can have it going low in the background and lose the headphones.
Getting the adapters was 1/2 the battle here – the 2.5mm mono out is super non-standard. I went to the local Cables & Connectors store which could only supply a 2.5mm stereo, which kind of sort of worked but not really (was a little flaky) – I ended up (as always) finding exactly what I needed at Amazon (2.5mm mono to 3.5mm stereo) and while I was at it, picked up a couple of 3.5mm stereo to 1/4″ breakout cables which I seem to be wanting every other time I pull out the mixer these days (record out to the TASCAM, line out from phones and tablets). I have a bunch of 3.5mm to RCA breakouts but the 1/4 is a lot more mixer friendly.
I like to support local retail when I can, but I’m invariably looking for something a little weird or left of center and rather than drive around all day for something that almost works, just pull up the exact right item on Amazon, order via Prime, and it shows up 1-2 days later. Probably better for the environment as well (considering my gas).]]>
Would you be pissed off? I suspect the answer is yes.
Happened to my employer this week. I’ve been doing their exit sign and emergency exit testing for a few years now – a monthly quick test (push the button, works for 30 seconds, pass / fail) as well as a more involved annual test (kill the building power for 90 minutes and make sure the lighting batteries hold up). I replace the batteries and/or lighting units as needed. I last did the big annual test in July 2018, and dutifully punched out the little official stickers that I purchased to make it all official.
This week, I noticed that one of those big industrial service companies was in to inspect the fire extinguishers, and somehow convinced the facility manager that she needed an annual electrical inspection (they may have actually sold her under-coating and floor mats while they were at it). So all of my little stickers were removed, replaced with theirs, even though the stickers clearly indicated that an annual test had been done in July 2018, two months prior.
Unethical = check. Sleazy = check. And to add insult to injury, there is no way in hell they did a full 90 minute “annual test” in the time they were on site – I suspect they did a quick push-button test. Potential criminal liability there. The funny thing is, the only reason I noticed was that they slapped the stickers on the front panel of the devices (rather than discretely along the side where my stickers were) so I spotted them as soon as I walked into the facility. So add “sloppy and lazy” to the descriptors.
We’ll be going back to them once the invoice comes in to get the charges reversed. And if that is ineffective, we’ll be sending a letter of complaint to the town fire inspector, as well as the state dept of consumer protection.]]>
Not a super serious issue, this time, but interesting to come across a timer based system. They seem to be increasingly rare as more sophisticated controllers are brought online each year.]]>
We are pleased to let you know that we announced the commercial availability of two new PQube® 3 models.The range of PQube 3 analyzers now includes:
Features of the PQube 3 analyzers include:
Benefits of using the PQube 3 analyzers include:
Read the full press release here.
I’ve been a fan of PSL Founder Alex McEachern from back in the BMI days; have not had a lot of opportunity to work with the PSL devices / technology. To be honest, without an on-staff or on-call power guru (like me) to help sort out signal from noise, the technology seems a little hard to use / parse for the layperson. But cool as hell, from a power quality perspective….]]>
For a while now, we’ve had a 1TB D-Link mini-server, dual parallel drives, serving as a backup device. It’s been getting full – so we decided to review and revamp. Turns out a big chunk of that drive (700 GB, at the moment) is devoted to one client, and an archive of site data and reports that go back nearly 15 years. In the early days the data sets were relatively small (by today’s standards) – 10 or 20 MB maximum. But today, we regularly see data sets that exceed 1GB.
So, new plan, we picked up a relatively low cost, 4TB backup drive (USB connection) and are moving all of the customer data over there. There’s no real requirement for this data to be backed up permanently, it’s more of a “nice to hang on to” archive. That way, we can free up the 1TB drive (still nicely serviceble and redundant as an automated backup device) for everything else.
What this requires, however, is patience. In the process of copying 700GB of data from the network drive to the USB drive is taking some time (days really); it’s slowing down my main workstation a bit but not enough for me to set up something else to handle the chore.
Once the data gets pushed to the new drive, I’ll clean up the old backup drive, and also clear out some space on my main workstation and spend some time defragging the disks.
MCM Electronics, in business for 40 years, will close two plants and its corporate headquarters in Ohio and lay off more than 90 workers, the Dayton Daily News reported earlier this summer. The company, which carries an electronics inventory of more than 300,000 items, including 3-D printers, tools, wire, cable, and other items, has been a Dayton Hamvention® vendor.
The layoffs will begin at month’s end and continue through the end of the year.
You can now find the MCM Electronics catalog on the Newark.com site:
MCM Electronics and Newark element14 have partnered together for over 32 years as part of the Premier Farnell family. Now, MCM will be strengthening this partnership under the Newark name. MCM’s unique product offering combined with Newark’s vast inventory, expanded services and global reach makes us the one stop shop for engineers, installers, educators and makers.
MCM Electronics and I go back a long ways. I’m pretty sure my first purchase was a set of Spin Tite nut drivers; I’d found them super handy in the labs at my first job at Superior Electric and soon after purchasing my first home I outfitted a workbench. Still have that small set of color-coded, english gauged drivers. Over the years I bought oddball tools and test equipment, parts and components, and most recently audio-video equipment. I’ve got a storage locker full of A/V gack: LED Par Lamps; speakers, speaker stands, lighting stands, lighting truss, XLR and speaker cables. Often purchased via one of the seemingly insane 50% off sales that would periodically flood my physical mailbox. MCM Electronics seemed to be one of the last bastions of physical catalogs; I still have their last catalog on my shelf.
It was never the highest quality stuff, but it was light duty, serviceable, good enough for my needs.And for whatever reason, their shipping department seemed to be amazingly responsive – I’d order stuff “slow boat” and it would show up 1-2 days later; big boxes of speakers or truss or whatever.
And while stuff still seems to be available, I have no doubt that the selection will narrow, the catalogs will stop coming, the to good to be true sales prices that often enticed me to buy will no longer be offered.
End of an era. There’s a lot of that going ’round in my world these days….