AD584 voltage reference and new meters.
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- Опубліковано 12 січ 2017
- re-upload of the original video which somehow disappeared in UA-cam abyss. In this video I test my old and new meters using two voltage reference boards with AD584 chips. To my surprise, the cheapest of the three meters tested is the most accurate in these measurements.
AD584 voltage reference
www.banggood.com/AD584-4-Chann...
www.ebay.com/itm/KKMOON-High-P...
Victor 86C
www.ebay.com/itm/VICTOR-86C-3-...
Mastech MS8268
www.banggood.com/Mastech-MS826... - Наука та технологія
I bought 4 b-side mini meters, drilled a hole in them behind VR1, bought a £60 10 volt precision ref voltage ref and then calibrated them with their cases on. TBH they were only a couple of mv from the ref. Much better than I expected. Good accuracy is handy if you are messing around with batteries, and it's nice to have all your meters to within a few mv of each other.
If the vendor lists the chip used in the voltage reference, the AD584L (now discontinued) came from the factory trimmed to +/- 5mv on the 10V range and slightly better on the other ranges. That's 9.995V to 10.005V and most meters under $50 don't read that many digits. The other AD584's are trimmed to +/-10mv or +/- 30mv at the factory.
For most of my 12V solar system work, I use a bottom-of-the-line Harbor Freight meter because it has an internal calibration pot that I can adjust to get the meter to 10.00 volts when reading an AD584L. I can check/calibrate the meter as frequently as I choose and if the meter gets dropped 20 feet it's not a great loss (under $10US).
I do have some better meters (including clamp-on AC and DC ammeters) but much of the low voltage work only needs the ability to check battery voltage accurately.
The meters are probably in spec because you need to consider accuracy of the meter in % and usually +/- one count.
Connect only one meter at a time for accurate measurements. Every meter has an input impedance which are then in parallel and have an effect.
I received one of these today with an identical calibration certificate.
That is what I like about my meter, I can shut off the auto off feature. Then it will stay on until the battery goes dead.
If a multimeter has a rs232 option, enable it to disable the auto-power-off. ;)
I know it is a old video, but maybe this information is still useful for someone...
Read the manuals, most meters the auto shut down can be overiden by holding one of the buttons when switching on. Bob UK
Bugger - I too have the fake measurement slip! Just for kicks, IF the measurements were authentic, what would the higher voltages (42V, 37V etc) have meant? The chip can only handle a maximum of 30V power supply so the voltages don't make sense.
Your Test would have been more accurate if you used the same probe set with all meters. As stated below the Transfer Calibration document that came with the one Reference Source is just a Clone. Best bet is to just go with the IC manufacturers Accuracy or Tolerances in hopes the chips are not also clones. The AD584 comes in various versions with different accuracies. The L version being one of the better.
Model AD584J AD584K AD584L
Min Typ Max Min Typ Max Min Typ Max Units
OUTPUT VOLTAGE TOLERANCE
Maximum Error1 for Nominal
Outputs of:
10.000 V 630 610 65 mV
7.500 V 620 68 64 mV
5.000 V 615 66 63 mV
2.500 V 67.5 63.5 62.5 mV
dmv’s usually spec +/- 1 digit.
I think you need to learn how rounding of decimals work. Hint: You do not just cut off the least significant digits, you round them up or down depending on which side of 0.5 they are...
I'm quite familiar with that concept. I grew up using decimal/metric system. For the purposes of this video and the precision needed, what i did was close enough. Rounding up or down when meter's precision is +-x% + x digits makes little difference. But thanks for your comment.
It is well known that the module with the jumpers has a fake sheet delivered which is the same sheet and the same values on all the same delivered modules so of course the values are 200% false !!!
I do not take anything Dave Jones says as correct, most of his comments on test equipment is very misleading.
For the 2.5V reference, I'm thinking maybe the meters are correct and the standards from China are lying. How do you know whether they are using authentic parts?
Who knows. These may be legit parts stolen from factory, quality control rejects or outright fakes. One thing for sure, whatever calibration measurement sheets they come with are fake. Wish i had access to calibrated high accuracy meter to check.
Its all relative
I think that Einstein proved that.