Fluke 28II  and Agilent U1272A can do pF cap measurements. - Page 1
Forum section: electronics / general

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: October 11, 2011, 02:39:51 pm
content: I feel a bit of shame writing this thread, but I do it because I must to.When I got those DMM units, no one came with the sort cables (banana to crocodile leads ).I did try to measure low value capacitors 10 – 100 pF with the test leads and I failed to get any results.And I thought that this is how those DMM act and that’s all about it.Yesterday, a very good friend of my came to me with one fresh UNI-T 60,so to perform to it a fast calibration check, and find out how it behaves (speed tests).Even if this specific model did not had capacitors measuring function,It did come with those small cables with shrouded banana and crocodiles’.I ask from my friend to offer them to me as gift because it was not useful to him in any way.And he did it with out a second thought. ( Thank you Sofos )As soon he left I start testing them, so to see if they do make the difference,and they did …I have take pictures, the Fluke 28II has poor resolution for the job and so I added one more imaginary digit.But even so it works !! ( at list for a rough estimation of the pF value )The Agilent U1272A for the first time after all those months,It did show pF with major accuracy and detail.I feel happy and stupid, but it was not my fault,I never got tiny leads, and never think that those high quality leads made by Fluke or other nice quality leads,will actually block the pF measurements’!!The sum:My apologies to Agilent .. because I was thought that U1272A can not do that pF measurement.My apologies to Fluke .. for the same reason.My thanks to my friend Sofos ( donor of those UNI-T cables)And finally I like to thanks my own curiosity, because with out it I would never realize, how important it is,all the fresh Fluke and Agilent DMM to be shipped with this low cost accessory asstandard.Today it looks very ridicules that they do not doing that !!And the list that they should do , is to write this detail in the Users Manual !!Please do it !!Or give to us the damn cables !!

author: zaoka
author_rank: Frequent Contributor
timestamp: October 11, 2011, 03:37:25 pm
content: Did you ever try to check how accurate is temperature measurement with Agilent?My body temperature with Agilent U1272A is 33.4C, with regular temperature meter it is 36.6C.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: October 11, 2011, 03:45:05 pm
content: Temperature measurement can be accurate to the point that the probe it self will aloud.Never see so far an specialized DMM probe for human temperature !!If they ever made any, it will limited to 0 up to 60C, so to be equal in accuracy,with the ones that gets sold in the pharmacy shops.

author: Unknown
author_rank: Unknown
timestamp: October 11, 2011, 04:51:17 pm
content: Quote from: zaoka on October 11, 2011, 03:37:25 pmDont forget that the DMM is measuring the temperature of the sensor (plus some errors), not the temperature of your body (which also varies by location).Quote from: Kiriakos-GR on October 11, 2011, 03:45:05 pmThey are fundamentally the same. The trick is to bring the sensor up to the same temperature as the material to be measured. In a thermocouple the connecting leads act as a heatsink for the sensor introducing large errors. As an example, temperature measurements in gases cannot be performed accurately with a short-leaded thermocouple as the sensor-lead thermal transfer is comparable to the gas-sensor thermal transfer. LASERs are used for precision gas temperature measurements.

author: BravoV
author_rank: Super Contributor
timestamp: October 11, 2011, 05:21:18 pm
content: Looks like you haven't read the meter's specification, I thought you did review one of them ?Its stated the range for capacitance measurement is from10nFto 10mF, everything under 10nf will not be considered as an accurate measurement.The reason is measuring under 1nf or at few pF level will not be accurate using that kind of method, even using that short cables like yours, just try yourself with 2 pieces of wires like only few centimeters length and twist them together, sometimes with the "right" dielectric material, they will formed like a cap that will have few pF by it self.Meaning, that short probe's cables them self will be acting as a capacitor and will definitely screwing the accuracy at pF level.Get your self a decent LC meter if you need an accurate capacitance under 1 nF, these meters are not designed to give an accurate down to pF values, that is why they're not providing that kind of short probes which is pointless and looks silly too.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: October 11, 2011, 06:25:26 pm
content: About the Agilent DMM, I had confirm before even posting the topic.That it measured correctly 10pF 33pF 56pF & 82pF .Those proofs, made me to believe that it does do the trick nicely.Speaking about accuracy, like comparing identical capacitors for 100% matching,yes the U1272A can do that too.About the term of the highest accuracy, I do not care about that, that much, because I do not need it.

author: jarvis
author_rank: Contributor
timestamp: October 13, 2011, 12:47:26 am
content: UT-61E can make it also.