How good DC voltage standard do you need? - Page 1
Forum section: electronics / testgear

author: implor
author_rank: Regular Contributor
timestamp: February 01, 2024, 08:47:44 am
content: I have the opportunity to buy a DC voltage standard for ~350USD.It has +/- 0.02% on all ranges (10mV-10V and 1mA to 100mA).My question is if 0.02% really is good enough for calibrating anything other then $10 multimeter.Main goal was to have it for calibration but of coarse there is other uses.What do you say? worth the investment or not?

author: tggzzz
author_rank: Super Contributor
timestamp: February 01, 2024, 09:19:34 am
content: Quote from: implor on February 01, 2024, 08:47:44 amOnly you can decide cost-benefit tradeoffs.Your spec is inadequate: it should also include drift over time and temperature.Most importantly, is traceability required, and what is the penalty for an incorrect calibration?

author: implor
author_rank: Regular Contributor
timestamp: February 01, 2024, 09:27:20 am
content: That is true.Main thing is peace of mind for myself that my instruments arewithin reasonablevalues.I may have to think more about what i need and want.

author: J-R
author_rank: Super Contributor
timestamp: February 01, 2024, 09:44:34 am
content: Just taking the accuracy spec at face value, you're basically spot on, maybe good enough for a 2,000 count DMM. Anything higher and your last digit on the DMM will not be valid.The $90USD LB01/LB02 published specs are 0.025%+1 digit (although only 24mA).So $350 seems a little steep by comparison, but real world performance is unknown.One issue is that test equipment can frequently be far better or worse than the specs. For popular products, you can get an idea of what to expect from other forum users.From mostly a practical perspective, I'd suggest buying a decent bench DMM that you can get calibrated regularly instead. Generating stable voltages and currents is actually very trivial in my opinion, but you need an accurate DMM to go with along with that.

author: Wrenches of Death
author_rank: Regular Contributor
timestamp: February 01, 2024, 07:15:20 pm
content: Quote from: implor on February 01, 2024, 09:27:20 amBINGO!WoD

author: tautech
author_rank: Super Contributor
timestamp: February 01, 2024, 07:27:22 pm
content: Is this not enough ?https://dmmcheckplus.com/

author: J-R
author_rank: Super Contributor
timestamp: February 01, 2024, 10:15:22 pm
content: The DMMCheck Plus is nice especially if you're in the US. Yearly calibrations are easy and cheap. Outside the US I think it's a bit more expensive. My main concern in the context of this discussion is that it is only 5V and 1mA.Some older gear that might be of interest: Ronan X86/X88 and Advantest R6144. Both are easy to DIY calibrate/adjust.

author: alm
author_rank: Super Contributor
timestamp: February 02, 2024, 12:00:18 am
content: Quote from: implor on February 01, 2024, 08:47:44 am0.02% should be plenty for 3.5 digit meters (cheap or expensive), and for some 4.5 digit with proper guard banding. Fluke 87 is 0.05% so could be done, Fluke 189 is 0.025% so could not be calibrated to factory spec but would be a good confidence check.The bigger question is in my mind how do you know it's in spec and how will you know it will still be in spec a year from now?

author: MathWizard
author_rank: Super Contributor
timestamp: February 02, 2024, 02:09:03 pm
content: I have to draw a line at some point, and avoid getting big bulky equipment like old voltage standards, it would be nice, but I should plan to have all my good equipment re-calibrated some day.But yeah for quick sanity checks, I should buy or make some little reference box. I can't remember the chip name, but I have plans for this somewhere, with some $10-20 chip that was in some good 1980's DMM's.Then there's ones like this, they make a current refence too, and other nice projects. I haven't tried any yet, but I should save some money and get some parts for a few like these.http://www.scullcom.uk/category/projects/precision-voltage-reference-box/

author: mawyatt
author_rank: Super Contributor
timestamp: February 02, 2024, 02:30:40 pm
content: Here's something we did awhile back, more as a "sanity" check for our DMMs than anything else. We labeled the file as DVM Calibrator, but obviously not good enough for any serious use as a "Calibrator".To make a quick DMM sanity check, we just used Banana Plugs directly on the PCB as shown.https://www.eevblog.com/forum/testgear/ac-rms-dmm-tests/Best,

author: zepto
author_rank: Regular Contributor
timestamp: February 02, 2024, 08:53:22 pm
content: .02% accuracy over what time period? What are the stability specs? What are the noise specs? What is the setting resolution? 10v seems quite limiting, imo. $350 seems a lot from the limited info you gave.Older voltage standard might have .05% annual accuracy but .001% hourly stability...aliexpress garbage not superior to these devices, despite volume of youtube shills.An uncalibrated and inaccurate but stable source can be useful when combined with an accurate, calibrated measurement device.

author: fourfathom
author_rank: Super Contributor
timestamp: February 02, 2024, 09:24:55 pm
content: I'm not doing *any* voltage/current measurements that require any particular accuracy, but as an occasional check I grab all my DVMs (usually three or four, all hand-held, ranging from Fluke to cheap Amazon Chinese, from 1 to 40 years in age), and connect them in parallel to measure the output voltage of a bench power-supply, or in series with a resistor to measure the current. As long as they agree reasonably well I am happy. If one is a big outlier I won't use it when it matters.