DMM reading differences

Other Hardware Science and Measurement
1

Dear All,

for my lab, i'm building a 4 channel power supply, with two digital DC buck converter (0-36V) and two analog (from different suppliers) XL4015 with display DC buck converter (1.2 to 36V) .

I have two DMM, one Fluke and one ordinary.

By turning on, i get differences, where the DC converter show 14V5, the Fluke shows 14V8 and the ordinary shows 14V7 as example.

And these differences appears on all 4 channels (buck converters).

Is this normal, a difference of 2% to 4% by measuring what the buck display and what the DMMs shows?

Thx in advance!

2

What is the accuracy of the buck display?

3

Nothing is perfect in the analog world (including the analog-to-digital converter built into your meters).

Do you have the specs for the meters? My Fluke at work is specified as 0.5%, +2 counts on the DC range. It gets calibrated once a year by an outside calibration lab.

14.7 & 14.8 is a difference of one-count (if that's all the resolution you have). And you might be on the "hairy edge" between two counts.

I assume the display built-into your DC-DC is "approximate" with no actual accuracy specification.

The Fluke is not "ordinary"? :stuck_out_tongue:

4

accuracy: 99.9 analog one: https://www.aliexpress.us/item/3256806128273195.html?src=google&src=google&albch=shopping&acnt=708-803-3821&slnk=&plac=&mtctp=&albbt=Google_7_shopping&albagn=888888&isSmbAutoCall=false&needSmbHouyi=false&albcp=20268592310&albag=&trgt=&crea=en3256806128273195&netw=x&device=c&albpg=&albpd=en3256806128273195&gad_source=1&gclid=Cj0KCQjwwYSwBhDcARIsAOyL0fgU6Y5SaC28nmjqut_yCXjiniuM7qcpjHlOScFI5szfbj2YkpKbSmcaAhtlEALw_wcB&gclsrc=aw.ds&aff_fcid=2bc7c5a54748453e8f468cae11fe4717-1711383908389-03835-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=2bc7c5a54748453e8f468cae11fe4717-1711383908389-03835-UneMJZVf&terminal_id=d86b766b23734a4298c42aba961baf84&afSmartRedirect=y&gatewayAdapt=bra2usa

programmable dc: 99.99 https://www.aliexpress.us/item/3256805274980513.html?spm=a2g0o.detail.pcDetailTopMoreOtherSeller.3.6fd4ksrLksrL0q&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40000.327270.0&scm_id=1007.40000.327270.0&scm-url=1007.40000.327270.0&pvid=f551c334-e4ee-4cd8-be7b-171d42a64a71&_t=gps-id:pcDetailTopMoreOtherSeller,scm-url:1007.40000.327270.0,pvid:f551c334-e4ee-4cd8-be7b-171d42a64a71,tpp_buckets:668%232846%238112%231997&pdp_npi=4%40dis!USD!26.04!12.76!!!187.62!91.93!%402101c5bf17113839606783954e7cfb!12000033175943206!rec!US!127740629!&utparam-url=scene%3ApcDetailTopMoreOtherSeller|query_from%3A&search_p4p_id=202403250926007304053054150888182085_2

5

My Fluke is a 8024B, an old and trustfull dog.

6

Believe the Fluke. If you are worried about these differences get the meters calibrated. You also need a decade more in your measuring device then what you are measuring.

7

the main question is if such a difference makes difference when feeding prototypes while building. :wink:

8

They could if you are powering at the targets voltage limit.

9

i didn't get it right. as far i know, there is a small tolerance, i.e 3V3 on ESp32 can handle from 3V0 to 3V5, or am i wrong?

10

The absolute difference is comparable, but the relative difference is not...
3V0 3V3 is a 10% difference....
Your meters are much closer than that. So: do not worry!

11

For that part you are correct!

12

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