Voltage / resistance reference - Page 1
Forum section: electronics / beginners

author: Teti
author_rank: Regular Contributor
timestamp: July 03, 2020, 10:45:39 pm
content: Hi guys, I'm wondering... are these cheapo AD584 eBay / Aliexpress voltage references any good? Also some decent resistor reference.I'm consider of purchasing one of the for starters to have at least remote idea of accuracy of my test equipment.I understand you can buy very decent one for 200USD, but are these cheap ones any good?These seem to caught mywalleteye...https://www.ebay.co.uk/itm/233350172172https://www.ebay.co.uk/itm/311498494419Go for it or avoid and get something more expensive boutique reference?Thank you for your answers and suggestions.

author: magic
author_rank: Super Contributor
timestamp: July 04, 2020, 05:59:53 am
content: There were threads about those Chinese AD584 boards, look around.IIRC they were mostly found to work okay, but these are recycled chips so there might be some risk of damage by desoldering at excessive temperature or other careless handling.editThe spec of that lowest J-grade also is what it is, see the datasheet for details.

author: tggzzz
author_rank: Super Contributor
timestamp: July 04, 2020, 08:41:52 am
content: Quote from: Teti on July 03, 2020, 10:45:39 pmYes, repeat no.In other words, that's the wrong question.A better question is "are they good enough?". That requires you to define "for what".

author: MosherIV
author_rank: Super Contributor
timestamp: July 04, 2020, 08:47:54 am
content: No - if you want a known calibrated reference. As magic has said, other discussions have shown that they do NOT individually calibrate (measure and record) each unit.Yes, if you cannot be bothered to build your own AD584 and measure it against a calibrated dmm. Buy one and measure it with a calibrated high precission dmm.I bought a AD584 chip and built my own. Just needs psu and circuit board. I had an old linear psu from a dead wall wart and just put it on perf board, then put it in a project box. Costs more than just buying on from ebay

author: Teti
author_rank: Regular Contributor
timestamp: July 04, 2020, 12:25:02 pm
content: Thanks guys, looks like I will have to save up for Ian Johnston's unit thenI don't even have decent DMM at the moment apart from £50 Extech unit, so I guess my issues are a little bit premature.

author: Teti
author_rank: Regular Contributor
timestamp: July 04, 2020, 12:26:46 pm
content: Quote from: MosherIV on July 04, 2020, 08:47:54 amI would build my own i I've had access to some decent DMM. And send it to calibration lab would be probably bit OTT

author: radiolistener
author_rank: Super Contributor
timestamp: July 04, 2020, 07:00:54 pm
content: most of them are fake or just remarked IC with worse precision and high temperature dependency. It's better to buy good reference voltage IC from reliable source and made your own reference voltage. It will be cheaper and you can believe that it has voltage according to specification.

author: tggzzz
author_rank: Super Contributor
timestamp: July 04, 2020, 07:05:48 pm
content: Quote from: radiolistener on July 04, 2020, 07:00:54 pmBut make sure you take account of the initial accuracy, tempco, and drift over time. There is a reason that voltage references are aged before they are measuredAnd when you know you have to take account of the Seebeck effect (i.e. draughts and temperature gradients), you know you are in voltnut territory. Hence it being important to know "good enough for what"!