Electronics > Metrology

Chasing PPMs? Put that cell phone away!

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CalibrationGuy:
So I wanted to take a few pictures of our 732 array, and was reminded of something I would tell all my lab techs. PUT the stupid phone away! Here's what happened to a measurement I was doing to test a newly acquired 732a with our most stable reference (also a 732a).

Those peaks occurred when I moved close to take a picture of the "flatness" of the test. So yes, these measurements can be affected by your (and your cell phone's) presence.

Picture...

TomG.

Andreas:
Hello,

Not only mobile phones. Also (even unused) USB-cables near measurement setup
can be a source of unexpected measurement deviations. E.g. here:

https://www.eevblog.com/forum/metrology/lowest-drift-lowest-noise-voltage-reference/msg3738565/#msg3738565

with best regards

Andreas

EC8010:
And switch-mode power supplies to laptops. I've twice chased red herrings before remembering to unplug the laptop's power supply.

ITArchitect:
Ah, chasing noise can be fun sometimes.  I found a similar issue with EMI coming from a wireless phone charging stand.  Pulled my favorites scope apart thinking I had issues.  Since then, all mobile devices have been banned from the lab.  |O :scared:

mendip_discovery:
What would be these PPMs you be talking of? Surely you mean ┬ÁV/V.

My MD was harping on that I should be doing TikTok videos, this in front of the 17025 assessor. He didn't notice my comment about TikTok users being mostly kids and creepy old men. I feel the need to draw 4 red perpendicular lines, some with blue in and some with transparent ink.

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