Comment on Calibrating vintage multimeter
BigDanishGuy@sh.itjust.works 1 year ago
Easy, you import this puppy www.ebay.com/itm/305042665748 and set up your own business offering calibration services to recoup the cost. Then you can apply for the calibration engineer position at Minerva.
Jokes aside, have you contacted a calibration lab? I don’t know what it’s going to cost, but I can’t think of another way, if you’re not going to built the sources yourself. There’s one in the Netherlands www.minerva-calibration.com/calibration-service/
It would seem from a quick google that I’m not alone in my conclusion. But at least I have found an article explaining the build of the sources you need wolfalex.bplaced.net/…/calibrator.htm
irdc@derp.foo 1 year ago
Their pricing for calibrating a device starts at around €400, which is rather more than I paid for this thing and way cheaper than building my own calibrator
Thank you! Not having to invent everything from scratch is going to make this a lot easier.
BigDanishGuy@sh.itjust.works 1 year ago
400? I guess that’s in the ballpark I expected it to be.
I haven’t studied the BOM for the DIY solution, but something tells me that you’ll only be able to keep the cost lower than 400, if you value your time at close to zero.
With all that negativity out of the way, I’d definitely want to build it myself too. Although my anxiety level is exponentially correlated to the working DC voltage and at 300VDC I’m definitely well in the thick rubbergloves territory. Be careful with the build!
irdc@derp.foo 1 year ago
Having been walloped by 230VAC, which is far more dangerous, I’m not too worried.
Looking at the schematic you linked above, the amperage is going to be low, which is reassuring. As a safety measure, I’m looking into running the thing off of a battery, so that if the worst comes to pass it simply won’t have the power to be dangerous (1A at 12V translates to a mere 40mA at 300V).
I’d be far more worried about using lead solder TBH (love my Sn100Ni+).
BigDanishGuy@sh.itjust.works 1 year ago
Well hello there Mr Edison, I didn’t realize the calendar read the 1880s again, please refrain from elephant ownership 😀 First off if you’ve got 300V I don’t care what form it’s in, I ain’t sticking my fingers anywhere near it! Secondly at least AC alternates, giving your muscles a break and possibly a chance to let go of the wire, DC isn’t that forgiving. The reason 230V AC is so dangerous is because it’s usually referenced to ground, meaning that if you touch a single wire, you’ll be drawing a current from that point and to your feet.
But that is all theoretical, because while 300V is stored, and the current may become quite high, it’s only backed by 100nF. Still, I’d want it discharged before poking about though.
The battery is a good precaution. Some of my co-students in university made an EKG apparatus. Our lecturer demanded that anything connected to the electrodes was to be powered by a single battery.
I may be a boomer in this regard, and I’m sorry for the rant I’m about to go on (that last part of the sentence was tagged on after writing the following). I prefer my Sn60Pb40 of which I got several kg from when it was outlawed, maybe throw in a little Ag in there for the 0.3mm SMD solder. TBH my love of lead solder may stem from the fact that I have more, in various diameters, than I’ll ever use.
The first couple of lead free solder brands I got just didn’t flow right. It didn’t help that the solder stations it was to be used with at work, by students, was old school Weller stations that just delivers a constant 24V AC to the iron, and the tips set the temp. All the tips we had were at a temp comfortable for lead solder.
But I digress… if you just wash your hands after soldering (and maybe use a bit of ventilation) then your absorption of lead is harmless ehs.harvard.edu/…/soldering_safety_guidelines.pdf