Why would you use your scopemeter for checking the calibration of the Centech meter when you have the 287? The 287 is >10x more accurate... lol. Scopemeters should only really be used for signals that change with time, on the 'scope' mode, or if you need an isolated input. Also, I could understand using the 'meter' mode on the scope meter if that's the only tool that you have. But, you've got a significantly higher performing multimeter right next to it, and you just set it aside... lol... makes no sense at all.
Wow, that CEN-TECH autometer is either damaged or severely out of calibration. The accuracy spec on the 20Vdc range is (0.8%+5). I'm reading that as 0.8% of the voltage plus 5 times the resolution, which is 0.1V on this scale. So your maximum value you should measure for a 15.25V voltage is approximately 15.88V. Something is very wrong if you are reading 21.0V.
"Within a few percent" I work for a Calibration/Certification Lab and the few percent is what you pay your money for. Really, the difference between Fluke, Gossen Metrawatt and other Pro Level equipment in accuracy, repeatability and build quality with cheap equipment is night and day. Do not risk your life, or your work, on cheap equipment, particularly when it comes to electrical work.
I got extech ma 1500 and all the potentiomerer had a v beside them come to find out there not all voltage they were amps .i had to buy whole other meter to get a rough calibration to dial them in and then i some messed the newiest one up .i was adjusting the voltage and the meter jas something built in it that makes voltage start drifting all over the placd .thought it was potentiometer so replaces potentiometer and it was still doing it and waited dor a couple hours and it started working again
Good video, thanks for posting. In the several years since this video was uploaded, cheap "True RMS" AC volt meters have been marketed. For low voltage AC measurements (filament) are they any good (1 decimal point or 10%) ?
The manufacturers of those cheap multimeter would have more knowledge and better calibration equipment than you to begin with...so if it does not accurate, it would not changes
It works for some , in some situations. If your checking if you have voltage AC or DC or if a car battery has a charge its sufficient but if your using it for controls work I would look at a better meter.
Good video. As for that Centech meter... I think the best course of action would be to discard it, rather than calibrate it. I've worked with both high end and cheap meters all my life and I have never seen a meter with a 9 volt deviation at 15 volts based purely on a low battery. Does it say in the literature that the Centech is accurate, plus or minus 40%? :) Seriously, I wouldn't trust that meter as a paperweight! Given it's tach and dwell ranges, it's obviously designed for automotive use. Initially, it was reading over 13volts with a 10volt input. This would definitely mislead an automotive technician in so many directions thinking he's dealing with a fully charged battery, when in fact he doesn't have enough juice to even crank the engine... Is it possible the voltage pot got knocked after you opened it up? If you're going to keep it and use it, I'd suggest using a variable power supply to power the meter and checking to see where it's readings fall with a low battery condition. If there is as much a discrepancy as you've shown in your video, the Centech meter must be using the internal battery as a measurement reference, which would be an extreme "no go" in meter design. Steve
For the vast majority of my work both personally and professional i only use high end meters, as a professional I do not have time to second guess my test equipment as do most people in a tech trade. I think the Centech has its place, certainly not in any professional setting. but for someone on a budget that is just getting into electronics I think it may be of use. High end meters usually have some form of brown out and black out protection, cheaper meters usually dont, so that would give a causality for the faulty readings due to low battery. But even my fluke 287 gets about 5-10% deviation in the reading when the battery gets low even before showing the low battery indicator so I do not believe any piece test equipment would be completely guarded against faults at low input voltage at least to some extent. I agree with you that an auto tech or any tech for that matter should not be using this meter trouble shooting. The voltage pot is fairy recessed and low profile, so the chances of me bumping it during disassembly is unlikely but not impossible . Like most things from harbor freights its a hit or miss, sometimes you get something of decent quality and sometimes you get a pile of junk so I may just got a bad that got skipped on QA or one thats been knocked and kicked around the store before purchase. I may have to make up a follow up video using a regulated power supply to feed the meter and see at what voltage the meter starts to act up and do the same with a low to mid range Fluke to compare the difference in brownout or low voltage conditions. Thank you for your insights and comments, please let me know what you think of my other videos.
Good sales pitch, like the garage near me say people think BMW are the best , there not they break down as much as any other car, but cost you a lot more to get fixed , all about the brand name sales, people think because there expensive there better , when in fact there not.
