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| Brand new Bm869s calibration |
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| Fungus:
--- Quote from: mrdave45 on February 19, 2021, 01:56:54 pm ---https://www.eevblog.com/forum/testgear/aim-tti-1908-5-12-digit-benchtop-multimeter-(preview)/msg3215950/#msg3215950 Maybe Ive just stumbled on the one post from the one person whos complaining about this thing. --- End quote --- Those meters aren't "far off calibration", they're within spec, they're just outliers near the ends of the bell curve on the production line. They'll be few and far between but if you're unlucky enough to receive one of those then a calibration certificate or fancy DMM check will only make you unhappy. Best not to get either of those. :popcorn: |
| Fungus:
--- Quote from: joeqsmith on February 19, 2021, 03:16:03 pm ---you get an idea on the price of these resistors and how tight they are. --- End quote --- I bought a used 10k resistor for $7 on eBay. It can read a bit low on a cold day like today (see pic). --- Quote from: joeqsmith on February 19, 2021, 03:16:03 pm ---I use that box to detect is a meter is starting to fail, not as a means to calibrate them. --- End quote --- Yep. It's fun when a meter/resistor/whatever appears to be perfect but it's really a bonus, not a garantee. The big problem is ambient temperature. Meters with lots of digits needs an internal heater for their references so they can be calibrated for a known temperature. You simply can't have that in a handheld (do you want a hot meter that chews through batteries?). |
| joeqsmith:
--- Quote from: Fungus on February 19, 2021, 03:30:23 pm --- --- Quote from: joeqsmith on February 19, 2021, 03:16:03 pm ---you get an idea on the price of these resistors and how tight they are. --- End quote --- I bought a used 10k resistor for $7 on eBay. It can read a bit low on a cold day like today (see pic). --- Quote from: joeqsmith on February 19, 2021, 03:16:03 pm ---I use that box to detect is a meter is starting to fail, not as a means to calibrate them. --- End quote --- Yep. It's fun when a meter/resistor/whatever appears to be perfect but it's really a bonus, not a garantee. The big problem is ambient temperature. Meters with lots of digits needs an internal heater for their references so they can be calibrated for a known temperature. You simply can't have that in a handheld (do you want a hot meter that chews through batteries?). --- End quote --- I had started logging some temperature data while looking at the drift. I think I figured about 3deg C change in the office but it's been a bit tighter than that over several hours. I used my HP34401A as a reference to align the Fluke after repairs. So again, absolute accuracy it a bit of an unknown but I would say in the ballpark. I ran a 10K ohm on the 40 year old Fluke for about a half day. You can find the datasheet for that resistor along with the data here: https://www.eevblog.com/forum/testgear/some-old-school-instruments-showing-how-its-done-(hp-3325a-and-fluke-8506a)/msg3462878/#msg3462878 |
| IanB:
--- Quote from: mrdave45 on February 19, 2021, 03:04:04 am ---I've been searching round the forum about the 869s and it seems there's quite a few comments about these being far off calibration out the box. --- End quote --- It may vary from sample to sample, but I was pretty happy with the one I received. See below: https://www.eevblog.com/forum/metrology/i-received-my-dmmcheck-plus-a-quick-test/msg1972838/#msg1972838 |
| IanB:
I can't guarantee you will get the same results, but here are a couple of pictures I captured in the past: |
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