one sick puppy, test equipment deviation. - Page 1
Forum section: electronics / testgear

author: tomy983
author_rank: Contributor
timestamp: January 29, 2016, 01:38:21 pm
content: Someone is not telling the truth... Which should I trust?

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 29, 2016, 01:45:31 pm
content: Both are correct if you include the tolerance. Fluke 80BK probe is 2.2C or 2%, whichever is greater.

author: tomy983
author_rank: Contributor
timestamp: January 29, 2016, 02:12:13 pm
content: Thanks, I never checked the fluke probe tolerance. I hope then that the regular thermometer (PIC) has better performance in the limited range it has to measures.This fluke probe at this temperature should be less than 1% off. Greate!It was actually the first time I used that probe, and it helped a lot justify the tool tho the wife

author: macboy
author_rank: Super Contributor
timestamp: January 29, 2016, 03:24:03 pm
content: Quote from: tomy983 on January 29, 2016, 02:12:13 pmNo, According to PAOPBZ, the tolerance is 2.2oC or 2%, whichever is greater. So below ~100oC, use +/- 2.2oC as the tolerance. Above 100oC, use +/- 2% of the reading. So at 38oC, the tolerance of +/- 2.2oC is equivalent to +/- 5.8% accuracy.The special purpose fever thermometer is specifically calibrated at body temperature and will have much greater accuracy in that range than a general purpose instrument that needs to cover a span of hundreds of degrees.Also, consider that for thermocouple measurements, there are two significant sources of error: The measurement of the thermocouple voltage, and the cold junction temperature measurement, usually done with a thermistor either inside the meter or preferably inside the thermocouple adapter. The thermocouple reading is added to the cold junction reading to get the actual temperature, so the errors are additive.

author: tomy983
author_rank: Contributor
timestamp: January 29, 2016, 03:48:05 pm
content: greater! That is what I've got wrong.Thanks also for the explanation of the error sources, that helps a lot understanding why such "high" tolerances..Definitely not the right tool for the job!Even though it perform better than expected.And me I was like: "let's get a better measurement here!"Fail!

author: Tim T
author_rank: Contributor
timestamp: January 29, 2016, 11:06:41 pm
content: Yes, Fail. But you now have a reason to purchase a more accurate tool.https://www.eevblog.com/forum/Smileys/default/smiliey_dmm.gif

author: hibone
author_rank: Regular Contributor
timestamp: January 29, 2016, 11:47:08 pm
content: Clearly the wife wasn't looking....

author: tomy983
author_rank: Contributor
timestamp: January 30, 2016, 08:34:19 am
content: The wife will never know!Well, obviously I have some thermal issues here. I am wondering if a couple of heatsinks on the forehead and a rubber band might do the trick..Hmmm...

author: VK5RC
author_rank: Unknown
timestamp: January 30, 2016, 08:47:53 am
content: Activate the major DUT's wonderful neural-hormonally controlled evaporative cooling system, supply paracetamol (acetaminophen) in correct mass dose.

author: Shock
author_rank: Super Contributor
timestamp: January 30, 2016, 12:47:39 pm
content: It's tolerance should improve with age, don't bin it yet, it might prove useful re-purposed as a lawn mower.

author: tomy983
author_rank: Contributor
timestamp: January 30, 2016, 01:55:15 pm
content: I think I'll keep him on service, even though he consumes a massive amount of energy and requires continuous recalibration. Pretty inefficient if you ask me!Btw, paracetamol seems to have fixed the problem, too bat cause I really wanted to try out the heat sinkThis sort of DUT seems to just fix themselves after a while, not much thinkering allowed