hybridfree/eevblog-posts huggingface dataset:
Soo.. do I need to send my new resistors already back to PTB for recalibration?  - Page 1
Forum section: electronics / general

author: mzzj
author_rank: Super Contributor
timestamp: February 14, 2019, 01:47:23 pm
content: Got a slightly used standard resistor set..Need to wait couple of years to calculate 100-years stability for these

author: Henrik_V
author_rank: Regular Contributor
timestamp: February 15, 2019, 04:32:18 pm
content: Very nice oneNext year (2020) will be the next puplic day at PTB, usually in September. It's every 2 years, so 2024 will matchPretty shure you will get at least some values in this case.

author: mycroft
author_rank: Regular Contributor
timestamp: February 15, 2019, 06:16:27 pm
content: You missed the 1.69 ppm change from 1990. Wait a little bit longer to not miss this year's change of -17 ppb

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 18, 2019, 09:15:32 pm
content: Don't forget the 1948 change-https://www.nist.gov/sites/default/files/documents/calibrations/87mscohm.pdfThat's fairly noticeable when having old resistors certified in a modern cal lab.

author: babysitter
author_rank: Frequent Contributor
timestamp: February 19, 2019, 09:44:22 am
content: Just want this thread subscribed.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 19, 2019, 10:35:02 am
content: How did they measure 0.000 099 99 in 1924?Impressive!

author: The Soulman
author_rank: Super Contributor
timestamp: February 19, 2019, 10:56:18 am
content: Quote from: Conrad Hoffman on February 18, 2019, 09:15:32 pmThat was the NBS (national bureau of standards, USA) Ohm that changed (490ppm) to better match the SI (systeme international) Ohm.Basically, the USA got it wrong and the pre 1948 was 490ppm to low.This Reichsanstalt resistor was likely unaffected by this.

author: Henrik_V
author_rank: Regular Contributor
timestamp: February 19, 2019, 12:42:51 pm
content: My eyes are old, and the picture not that clear.Do the calibration report and the resistor match?I read 36/1924 on the cal mark on the resitor (38/1924 in report)and the serial number looks close but the last digit seems 0 (1656740?? )and the 10 isn't for 10 Ohms?

author: mzzj
author_rank: Super Contributor
timestamp: February 19, 2019, 07:15:16 pm
content: Quote from: Henrik_V on February 19, 2019, 12:42:51 pmYou are right. I didn’t get the original! certificates yet and the example photos are not even from matching set. What really amazed me was that the original 1924 cal certificates were still together with the resistors.

author: Henrik_V
author_rank: Regular Contributor
timestamp: February 20, 2019, 05:06:48 pm
content: Quote from: mzzj on February 19, 2019, 07:15:16 pmWell, one major value of a calibration artifact is his known history. So you try to keep both together.
Calibration Lab Recommendations for LCR Meter - Page 1
Forum section: electronics / general

author: mr.fabe
author_rank: Regular Contributor
timestamp: February 16, 2019, 12:44:51 am
content: Hello,Does anyone have any recommendations on calibration labs that you've had good luck with servicing LCR meters? Price is always under consideration but sometimes one cannot be so choosy. I have a Keysight U1733C LCR meter that I would like to have calibrated. I've been starting to get crazy, out of the ballbark readings on caps. I crosschecked with other meters (Peak ESR70, LC103, LC75, MESR, Fluke 289) and the U1733C is the only one not even close. Can't trust it for now...Thank you

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 16, 2019, 01:05:45 am
content: Sounds like maybe it needs repair before calibration, so it probably has to go to Keysight. Their stuff rarely drifts very far even after years of use, so far out readings are suspicious.

author: mr.fabe
author_rank: Regular Contributor
timestamp: February 16, 2019, 01:55:10 am
content: Thanks Conrad,That makes sense that a repair may be due. Looks like I will have to tear it apart and do some basic checking on this unit. If I need to send this thing in for repairs, I need to make sure it's completely broken. It's amazing how these things breakdown right after the warranty expires...

author: DaJMasta
author_rank: Super Contributor
timestamp: February 16, 2019, 08:22:42 am
content: It may not be too bad to chase down the fault, since the board isn't super complex. When trying to diagnose what part of the thing is off early on, it helps to do a lot of testing to see exactly what's not right: just capacitance? all ranges? all frequency settings? etc.If chunks of the functionality still work, then the odds are reasonable that it's a supporting component that can be found and replaced. If it seems like everything is wonky, it points towards a more central part - the processor, a reference, voltage rails, a timebase, etc. Once you have your fault fixed then you can figure whether it's close enough to spec for your use case or if you actually want it recalibrated. If you get things that are way out of whack, especially if it happens quickly, then I'd also expect a repair is required, not just a cal. If you send it to Keysight, the repair will be either swapping the board or just swapping the meter entirely - unlikely they'd spend the time on component-level troubleshooting.

author: mr.fabe
author_rank: Regular Contributor
timestamp: February 20, 2019, 05:42:45 am
content: Update...Contacted Keysight and the repairs are unit swaps at $298 USD.Did some basic checks and found smd caps out of tolerance but that was in-circuit testing which I do not trust. I ordered replacements and swapped the caps. I retested the U1733C and it is now working as it should. I conducted a post-mortem on the 'bad' caps and they appear good. Crazy.Thanks to Conrad and DaJMasta for the tips!
Can someone identify the mains socket type required for Fluke 845AB {SOLVED} - Page 1
Forum section: electronics / general

author: LaserEng
author_rank: Regular Contributor
timestamp: February 16, 2019, 02:56:22 pm
content: I have recently purchased a Fluke 845AB but it came without a mains lead and I thought it wouldn't be a problem as it would just be an IEC plug on the backMy google fu has let me down and I haven't been to identify what type of plug I need to get or even if it is still made. The plug is shown of the picture of the back of the 845AB, hopefully someone can identify what type it is.

author: LaserEng
author_rank: Regular Contributor
timestamp: February 16, 2019, 03:35:29 pm
content: Closer picture, looking at it I think it's the same shape as the plug for plugging into standard american electrical outlets but I have never seen the plug on the back of a piece of equipment before. I'm thinking this has to be one of the NEMA standards.

author: ArthurDent
author_rank: Super Contributor
timestamp: February 16, 2019, 07:58:22 pm
content: In about the 1970s there were some pieces of equipment that used these connectors so all you needed in the U.S. was a NEMA extension cord. You would need a plug for your outlet style and to configure the line voltage to agree with your mains voltage.

author: floobydust
author_rank: Super Contributor
timestamp: February 16, 2019, 09:38:20 pm
content: There are Nema 5-15R toIEC C14adapters which might be easiest to use.Vintage Amphenol chassis-mount AC receptacles forNEMA 5-15Rplugs 160-11N use a round mounting hole, so I am not sure what make this square one is, to check its size.You can check if you have room to fit an IEC receptacle, the two mounting screws are you could file out the opening and drill holes. Need over 40mm. I dont see room for that unless on the other side of the fuseholder.

author: LaserEng
author_rank: Regular Contributor
timestamp: February 17, 2019, 07:42:57 am
content: Thanks for the replies, seems that Fluke changed from the NEMA plug to an IEC C14 in later units, as seen on photos of a 1992 unit on Xdevs website, mine was from 86.They had to move the fuseholder further to the center of the instrument to make room for an IEC inlet. Good to know there are adapters available from this NEMA standard to an IEC type, I will buy one of those instead of adapting the unit.
Induced noise from DMM? - Page 1
Forum section: electronics / general

author: zed65
author_rank: Contributor
timestamp: February 10, 2019, 08:12:31 pm
content: Hi, I measure a standard LT1021 5 volt reference and tested it against my different DMM:s (Agilent 34401A and HP 3457A). Below is screen cap from my Rigol DS1104.Is this noise "normal" to differ from those 2 meters? Are one meter more "noisy" than the other?

author: Andreas
author_rank: Super Contributor
timestamp: February 10, 2019, 08:34:51 pm
content: Hello,did you use fully shielded cable or a probe with a pig tail?Is your reference battery supplied, and kept in a metal (cookies) box.Are there any switchmode supplies near the measurement setup? (or LED lamps)How does the FFT spectrum look like. (I see the local FM stations in the spectrum when using non shielded cable).with best regardsAndreas

author: zed65
author_rank: Contributor
timestamp: February 10, 2019, 08:59:03 pm
content: Hi, I use "standard" BNC cables but my concern is why is the 2 meters show different noise levels (nothing else is changed) when i just unplug the 3457 and put the cables into the 34401.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 10, 2019, 09:16:32 pm
content: It may only take very minor changes to influence the RF reception. So it may be just a different load capacitance to cause a resonance. The first curve looks a lot like there are 2 dominant frequencies that are very close.So the FFT might tell a lot. Another point would be reading a really quite source like a 1.5 V battery.

author: zed65
author_rank: Contributor
timestamp: February 10, 2019, 09:55:00 pm
content: Hmm the FFT function on the Rigol isn't that great (or i may do something wrong).I will try with a 1.5v battery later.

author: zed65
author_rank: Contributor
timestamp: February 10, 2019, 10:11:50 pm
content: Here is when I measure a 1.5v AA battery.The meters are ontop of each other so I just swap the cable between the meters.Not that this is a problem, i'm just curious why this happen

author: David Hess
author_rank: Super Contributor
timestamp: February 11, 2019, 12:29:30 am
content: Depending on the design, digital meters generate various levels of charge injection at their inputs but measurement is tricky because of common mode coupling from ground to the meter's low side input. If your meters support it, try making the same measurement with automatic zero disabled.

author: SilverSolder
author_rank: Super Contributor
timestamp: February 11, 2019, 02:21:35 am
content: I have seen similar effects with my DMMs here (various older Flukes).Have you tried putting something like a 1K resistor in series with one of the test leads to see if that reduces the interference?
HP3478A reading zero on valid dc input after newbie "CAL" - Page 1
Forum section: electronics / general

author: VNUTDENYER
author_rank: Contributor
timestamp: February 05, 2019, 11:09:23 pm
content: Probably this has never happened to anyone on this forum and saw no place for goofs so here it is. Tried a rough cal on new to me HP3478A with D.Malone 3v ref (recently checked with 3458 by buddy). Seemed to go kind of rough with sticking in CAL mode and had to cycle power. Got done and checked ref and it read "zero's". Thought I had fried, some how, 3v range. Cables ok, front selected, tried everything - dead. Reversed polarity of ref and read -6v!! Turns out CAL firmware will not accept user data more than ~7%? from the value it "knows" but will take reverse sign!! Jumping in and out of CAL i must have entered 3v when it wanted zero. Redid slowly and all fine. Now need to bring "new" EDC 510J into the fold.

author: Tj138waterboy
author_rank: Regular Contributor
timestamp: February 07, 2019, 10:49:26 pm
content: It sounds like you put on a 3 volt reference when it was looking for the shorted reference. You can fix it by going through the calibration again making sure you are on the 3V scale. Attention to detail on the Volt ranges. I ruined my 3478a by being in the wrong range. I believe if nothing is attached you should see roughly - 3.000xx if you did it incorrectly on the correct voltage scale. Pretty much it was looking for 0.00000 short and you gave it 3v so everything now will be 3v less that what it actually is.
501J "stuck" switch/LED - Page 1
Forum section: electronics / general

author: VNUTDENYER
author_rank: Contributor
timestamp: February 06, 2019, 05:18:07 pm
content: Recent "good" buy on 501J due to 4sd "8" bit stuck on. Seller thought it was intermittent and probably the switch so took a chance. The switch pulls a 74158 input to ground to select that BCD input (8mv on 10v range). Swapping 74158 with another digit did not move problem and measuring at ic showed switch could not pull input to ground. Alpha work around was pull ic and just have that position dead, no output but no problem. Next was pull input to ground with 650 ohm and rest of switches work so only missing 8 and 9 mv. Next day pulled front panel and switch panel prepared to swap switches or flush it or whatever. Plastic toggle appeared jammed to one side and not capturing very short stub on switch. Properly installed toggle and all's well. Now needs "CAL" to limit of existing gear. If the LED is lit, that BCD selection is input to the dac. Pull the chip for no inputs or pull pin low to have the remaining 3 (in this case 1,2,4 for 4SD and 1-15 for 5SD + 6SD SO 1-8.65mv).

author: SilverSolder
author_rank: Super Contributor
timestamp: February 07, 2019, 12:53:53 am
content: Nice repair.These things are really very handy to have around.
[ASK] Symmetricom Datum box , is this just a GPSDO ? - Page 1
Forum section: electronics / general

author: BravoV
author_rank: Super Contributor
timestamp: April 08, 2019, 10:01:48 am
content: Attached below, can not find any reference on the net, probably my Google-fu is really inadequate.What is this ? Just a GPSDO with 10MHz distributor in a box ? Or something else ?Does anyone know / familiar with it ?

author: testpoint1
author_rank: Frequent Contributor
timestamp: April 08, 2019, 04:46:45 pm
content: seems it is a GPSDO, and the GPS board is quite old now.

author: EOC_Jason
author_rank: Contributor
timestamp: April 08, 2019, 09:39:53 pm
content: Yep, just a GPSDO...Before you use it, check the voltage on the antenna port... Some old symmetricom equipment liked to use 12V instead of the more common 5V...

author: BravoV
author_rank: Super Contributor
timestamp: April 09, 2019, 08:10:52 am
content: Quote from: EOC_Jason on April 08, 2019, 09:39:53 pmThanks, noted.
Efratom FRS-C locking behavior - Page 1
Forum section: electronics / general

author: tkamiya
author_rank: Super Contributor
timestamp: February 05, 2019, 06:23:05 pm
content: I have several FRS-C and I'm concerned about one of them.All units lock fine. Most of the time, it gets the lock in 3 to 4 minutes, lock signal flickers 1 to 2 times may be then stays locked.One unit in particular, on cold boot, it gets the first lock in 3 to 4 minutes, loses it, takes about 1 minutes to get a lock again, flickers, does back flips, flickers, and finally locks. This gyration may take 3 additional minutes or so. Once it gets a firm lock, it is locked solid. On warm boot, it locks like all others: one or two flickers at the most.Does this seem normal to folks with more experience than I? I am trying to decide to keep it or return it.

author: Johnny10
author_rank: Frequent Contributor
timestamp: February 05, 2019, 07:22:55 pm
content: Tap on the side of the case lightly while it is locked and see if that knocks it out of lock.I have had a few do this and they eventually stop locking altogether.Generally my experience has been the same as yours.On FRS-C units

author: texaspyro
author_rank: Super Contributor
timestamp: February 06, 2019, 05:12:01 am
content: It could be wonky electrolytic caps. The LPFRS (among other) Rb's are known to have caps that have degraded. Particularly well known are blue Phillips caps.

author: tkamiya
author_rank: Super Contributor
timestamp: February 06, 2019, 05:17:01 am
content: Oh, oh....Come to think of it, my last one died exactly this. Seller is agreeable to return/refund, so I will take this route. I don't need an unreliable master time source.OFF TOPIC but let me just tack this on, too.I also have FRS-C that are 10MHz SQUARE WAVE and 20MHz SQUARE WAVE. It wasn't my intention to buy these but seller sent a wrong one. Are there any advantage in keeping these? I was buying 10MHz sine wave kind.

author: capt bullshot
author_rank: Super Contributor
timestamp: February 06, 2019, 07:12:41 am
content: It might be in need of a bit of re-aligning the RF leveling loop.From my experience, the FRS locks a few minutes after turn on and stays locked. Unstable lock could be a result of too low an RF level fed into the rubidium cavivity.Look here:http://wunderkis.de/efratom-frs/If re-aligning the pots helps, you should consider to replace them, since this failure mode re-appeared after some time of storage.No electrolytics to wear out inside, in general the FRS-C is a quite long-lasting design. These pots appear to be a weak point. There's also some hints on how to regenerate a faded rubidium lamp.
Keithley 417K - Page 1
Forum section: electronics / general

author: syau
author_rank: Frequent Contributor
timestamp: January 30, 2019, 12:53:17 pm
content: Just grab a Keithley 417K from fleabay, noticed that it can take down to 1E-14 A but unable to find related document from google.Anybody have a manual for it ?I also get a 4160 input head to part out if needed.

author: VintageNut
author_rank: Frequent Contributor
timestamp: February 01, 2019, 07:29:16 pm
content: https://www.tek.com/manual/keithley-models-416-and-417-instruction-manual

author: syau
author_rank: Frequent Contributor
timestamp: February 02, 2019, 04:18:34 am
content: Quote from: VintageNut on February 01, 2019, 07:29:16 pmBut this manual not describe the 417K variant which have a different front panel

author: syau
author_rank: Frequent Contributor
timestamp: February 04, 2019, 10:09:23 am
content: The 417K has different multiplier ampers selector than the 417
Fluoropolymer Cross-linked Modified ETFE-XLETFE wire.. good for volts and ohms?? - Page 1
Forum section: electronics / general

author: acts238willy
author_rank: Regular Contributor
timestamp: February 05, 2019, 08:10:52 pm
content: Wire for sale on fleabay...Fluoropolymer Cross-linked Modified ETFE-XLETFEIs it better than teflon for volt and ohm hookups? Both are silver plated copper.Especially ohms, where the sutup could be more sensitive, like a 3458.

author: The Soulman
author_rank: Super Contributor
timestamp: February 05, 2019, 10:13:59 pm
content: What are your concerns, leakage thru the insulation or thermal induced EMF from the conductor?

author: acts238willy
author_rank: Regular Contributor
timestamp: February 06, 2019, 01:02:57 am
content: I want accurate volts and ohms.Some things like temperature will affect measurements.I want to hear about wiring effects on accuracy.

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: February 06, 2019, 02:02:03 am
content: Wire insulation only gets into the act with very high values, hundreds of megohms, gigohms and teraohms, the higher you go leakage becomes more problematic, guarding is often the best solution to ward off leakage paths. Look at some of the high ohmage resistor bridges and how they are constructed, this is nothing new, been around for decades long before Teflon.Thermal EMF is an entirely different problem between conductors and silver doesn't necessarily produce the lowest EMFs, matched metal to metal is the best, copper to copper, no exotics need apply.

author: acts238willy
author_rank: Regular Contributor
timestamp: February 06, 2019, 04:27:03 am
content: Thank you, Edwin! I know that Data proof scanners use copper telephone wire and they're goodfor sub-ppm measurements. Their newest offering does include shielding, for even better specs.I may try the plain copper wire cable on one channel and the silver coated shielded cable on the otherto see if there are any differences. I'm new to this Data Proof ppb - level measuring but I do havean SR104 10K and a 732B 10V, with some 3458s to measure with....
Thin PTFE heatshrink: is it of use to anyone here? - Page 1
Forum section: electronics / general

author: tggzzz
author_rank: Super Contributor
timestamp: January 24, 2019, 02:24:20 pm
content: I recently bought some uninteresting transparent tubing for general purpose insulation of hookup wires, but when I took some out of the packaging it felt unlike bog-standard tubing. On investigating the part number it transpires that it is more interesting PTFE heatshrinkI've more than I need, so is anybody here interested in some?It comes in 1m lengths, is easily kinkable, and the specs can be seen in the images or athttp://www.qscomp.cz/Pdf/Tfe.pdfThe images show a section that has been shrunk and one of my bits of hookup wire approx diameters 0.52mm/0.95mm. The wire was insertedaftershrinking, and is a snug fit.
Small gold crocodile clips - Page 1
Forum section: electronics / general

author: BigMark
author_rank: Contributor
timestamp: January 18, 2019, 09:02:45 pm
content: I have been looking for a source of 40mm gold plated crocodile clips. The only gold plated clips I have found are sold by Peak Electronic Design for their range test instruments.Anybody have any idea where these small crocodile clips can be found ?

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 18, 2019, 09:57:00 pm
content: The Peak ones seem to be the only game in town. Even searching for alligator clips didn't help much ;-) If you needed a lot of them you could probably buy copper and have them plated.

author: serg-el
author_rank: Regular Contributor
timestamp: January 19, 2019, 08:21:15 am
content: https://www.tesco.com/direct/maplin-40mm-gold-plated-insulated-crocodile-clip-in-black/463-3033.prd?source=others

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 19, 2019, 12:13:05 pm
content: In Japan, we have these which are really good, made in Tokyo:http://www.teishin-bel.co.jp/http://www.teishin-bel.co.jp/mokuji_kurippu/clup.pdf

author: BigMark
author_rank: Contributor
timestamp: January 19, 2019, 05:41:08 pm
content: Thanks for the replies. It seems nobody is making these any more as I did a extensive search and found nothing. I have managed to find some Kelvin type clips which are slightly bigger on eBay and these will do the job with some small modifications.

author: DC1MC
author_rank: Super Contributor
timestamp: January 19, 2019, 07:35:25 pm
content: My modest contribution:https://muellerelectric.com/product/a17bthe-gold-alligator-clip/https://muellerelectric.com/product-category/alligator-clips-insulators/alligator-clips-insulators-aa/

author: rsjsouza
author_rank: Super Contributor
timestamp: January 19, 2019, 11:29:22 pm
content: Quote from: DC1MC on January 19, 2019, 07:35:25 pmThe first one I saw on eBay for US$0.99 + shipping. However, I am not sure if this is a small clip.https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F192569559782

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 20, 2019, 08:31:23 am
content: How many do you need?In the links I gave above, C-101-5 is probably what you want. Gold plated and about 40mm long, with 6 colour choices.They are certainly being sold in Akihabara, I've bought heaps. Good quality parts, not like the cheap Chinese ones that are often misaligned and bend easily.PM me and we can sort something out to get a bunch your way if you want.

author: BigMark
author_rank: Contributor
timestamp: January 23, 2019, 08:14:19 pm
content: Quote from: TERRA Operative on January 20, 2019, 08:31:23 amThanks. But I have sorted a alternative option which will do.
[Resolved] BM235 Accuracy & measuring 6mV - Page 1
Forum section: electronics / general

author: Romain
author_rank: Regular Contributor
timestamp: January 10, 2019, 11:27:45 am
content: Hi allI'm planning to use my BM235 (2y old) to measure contact resistance in the order of a few mV.The contact should not exhibit more than 6mV of resistance when a current of 7A is passing through it.The BM235 spec is a 0.3% (+2d?) accuracy in the 60mV range, which should give 180µV acccuracy.First question: is that ±180µV or half that?And now the $1000 question:How can I check that my multimeter is actually calibrated? I've checked #374, but that's as unhelpful as it gets...Finally, would you think of another way of measuring this with a better accuracy using, say, a x10 op-amp? That would increase the SNR, assuming the op-amp is accurate of course. Am I getting this right?Thanks!PS: Obviously, if I could afford a Keysight 34470A I wouldn't be here asking questions

author: 2N3055
author_rank: Super Contributor
timestamp: January 10, 2019, 02:41:32 pm
content: Spec says +/- 0.3% of READING digits+ 2D.That is 180 microvolts at full range of 6 mV...At 6 mV it is +/- 0.3% ofthat+ 2D.So you should be fine with just BM235 for this task.

author: evava
author_rank: Regular Contributor
timestamp: January 11, 2019, 08:53:13 am
content: I beg to differ:Full range is 60.00mV.so, 1% of reading of 6mV is 60uV (0.06mV)so, 0.3% of reading of 6mV is 18uV (0.018mV)+2D, which is 0.02mV or 0.333% of every/arbitrary reading.So, on reading 6mV there is error +-0.633%, meter can show 6mV like 5.96mV or 6.04mV.Is that right?

author: 2N3055
author_rank: Super Contributor
timestamp: January 11, 2019, 10:38:53 am
content: Quote from: evava on January 11, 2019, 08:53:13 amI made a typo yes, it was meant to be :"That is 180 microvolts at full range of60mV.. +/-2D" Sorry.Quote from: evava on January 11, 2019, 08:53:13 amThe meaning of :"At 6 mV it is +/- 0.3% of that + 2D." is : +/- 18uV AND +/- 20uV noncorelated. Worst case error +/- 48uV . +/- 0.8% Max

author: Romain
author_rank: Regular Contributor
timestamp: January 13, 2019, 06:07:55 pm
content: Right, I understand now.How about the actual meter calibration?I have the DMM since June 2016. How to make sure it's still within specs?https://www.eevblog.com/forum/beginners/diy-voltage-reference-for-dmm-calibration/

author: 2N3055
author_rank: Super Contributor
timestamp: January 13, 2019, 06:29:58 pm
content: Unless you were very rough to it, it probably is..Do you know anybody with a 0,05% or beter meter ? Like Fluke 87V or 289, or Brymen 867/869.Quick check with simple PSU and both meters in parallel for volts, in series for current and few higher quality resistors are good sanity check to see if it's roughly there...No need to go crazy for 0,3% meter...Truth is, low precision handhelds rarely drift very little.. They are either damaged or stressed so much that they drift either visibly or they are in spec. Which is kinda wide anyways..
Fluke 5700A/5720A specifications - Page 1
Forum section: electronics / general

author: splin
author_rank: Frequent Contributor
timestamp: January 12, 2019, 02:50:38 am
content: I can't reconcile the specifications from the "5700A 5720A Series II Extended Specifications" document. I've attached the voltage uncertainty table for the 5700A. The problem is the uV adder which is to account for noise and DC offsets including thermal EMFs.Comparing the 24hr absolute and relative uncertainty columns the uV adder is identical in the majority of cases. The absolute uncertainties are specified for a temperature range of +/- 5C from calibration temperature and +/- 1C for relative uncertainties. The issue is that the uV adder are temperature dependent as specified in the second table so how can the absolute and relative figures be the same? Either the absolute figure must be too small or the relative one too large?The notes don't help:QuoteThat must also be included in the Relative Uncertainty values as well so why not say so?QuoteThat doesn't apply to the Absolute Uncertainties within +/- 5C because it is already included, but it must surely apply to the Relative Uncertainties values - unless the temperature coefficients are magically zero in the range +/- 5C?Fluke know what they are doing so where am I going wrong?

author: Kleinstein
author_rank: Super Contributor
timestamp: January 12, 2019, 09:36:19 am
content: For the added error in µV I see especially 3 sources: temperature gradients causing thermal EMF and as a second effect EMI related offsets. A third are errors in the zero adjustment, e.g. due to noise, but also the two cause before.The thermal EMF effect would depend more on internal differences and not the absolute temperature. So it's plausible to be a bout the same for the 1 and 5 K range around calibration temperature.The not on the temperature coefficient only applying above 5 K deviation is indeed a little odd, as the relative data are for +-1 K. It might make some sense as the first table give values for the +-5 K window.

author: TiN
author_rank: Super Contributor
timestamp: January 12, 2019, 11:44:40 am
content: Relative Uncertainty is mainly ACAL calibration error contributions to external standards transfer, when range adjustment is used. It is given in spec if you want to determine calibrator error with your artifacts uncertainty. Fluke can control what are internal rrrors contributors and correct for them to some extent, but has no control over what happens outside of calibrator with your external calibration references.
Acoustic spectra of sung vowels by the FFT analyzer HP 3561A - Page 1
Forum section: electronics / general

author: Physikfan
author_rank: Regular Contributor
timestamp: January 08, 2019, 07:41:45 pm
content: The acoustic spectra of sung vowels of several persons were recorded with a condenser microphone and the FFT-Analyzer HP3561A:In the first row the spectra for A, E, I, O, U are shown, person 1.In the second row the spectra for A, E, I, O, U are shown, person 2.In the third row the spectra for A, E, I, O, U are shown, person 3.Although the fundamental frequencies of the vowels of the first person (in the first row) are much smaller than those of the two children (in the second and third rows), the spectral patterns for the individual vowels are reasonably similar. This is due to the resonance characteristics of the vocal tract, where each vowel can be identified in specific frequency bands (the formants) due to its spectral distribution.
STPM32 current reading lower than multimeter reading? - Page 1
Forum section: electronics / general

author: jpmkm
author_rank: Contributor
timestamp: January 08, 2019, 12:53:20 am
content: I'm working on a power meter based on the stpm32(https://www.st.com/en/data-converters/stpm32.html), that I'm planning to use on on 24VAC loads at no more than about an amp. I've gotten to the point of being able to read RMS voltage and current(register 0x48). Using the formulas, I'm getting pretty close. With purely resistive loads I'm <1%(which is just calibration) off from my amprobe am-130. However, when I hook up an HVAC controller(which is why I designed the meter), I'm reading significantly lower current with the stpm32-based meter than with either the amprobe am-130 or a fluke 8808-a(both of which claim true-rms measurement). For example, with one controller, I was reading around 115-120mA on the fluke, and about 90mA with the stpm32. Why are the readings so different and which one is correct? I don't want to believe that the fluke is wrong, but I also don't want to believe the the stpm32, which is used in actual utility power meters, is wrong. The controller uses a half-wave rectifier(single diode) to a capacitor to the power supply, which I have a feeling has something to do with this. My stpm32 meter is using a low-side .01ohm current shunt, and 188Kohm/470ohm voltage divider for the voltage side. Voltage seems to be within calibration no matter what.Ultimately I'm not really concerned with exact current measurements - I'm more concerned when one controller I'm testing pulls more than the other hundreds that I've tested. But when my measurements are so different and I don't know why, I don't feel like I can trust a meter I designed over a fluke. Even though I think the fluke is being less accurate in this case, I can't explain why.
Looking for calibration procedure for an ESI Video bridge 2150.  - Page 1
Forum section: electronics / general

author: 1audio
author_rank: Frequent Contributor
timestamp: December 20, 2018, 05:37:19 am
content: I have 2 ESI 2110's and an ESI 2150. I have the manual for the 2110 but the 2150 is enough different that the cal procedure probably is not the same and the test points and trimmers are certainly different. Does anyone have the procedure or a scan of the manual they can share? I have found very little on the 2150 version but a complete scan of the 2100 version on line.

author: picburner
author_rank: Frequent Contributor
timestamp: December 20, 2018, 08:59:18 am
content: I have a good old ESI 2160 and the paper service manual of 2150/2160.I did a scan of section 4 only, "Performance, Calibration and Maintenance" but it is a bit too thick to put here (about 14MBytes).I can put it on the KO4BB website or send it at your email address.BR

author: ap
author_rank: Frequent Contributor
timestamp: December 20, 2018, 09:27:08 am
content: Putting these things on KO4BB is always a good solution.

author: 1audio
author_rank: Frequent Contributor
timestamp: December 21, 2018, 05:52:25 pm
content: I agree. Send to me (I'll pm my e-mail) and send to KOBB since the odds of me losing it are pretty high over time.

author: picburner
author_rank: Frequent Contributor
timestamp: January 06, 2019, 12:08:22 pm
content: For those interested in this service manual I sent 4 sections of the same to the KO4BB site.As soon as I find the time I will complete the work.
Datron 1281 turn displays off/on  - Page 1
Forum section: electronics / general

author: Fastah
author_rank: Contributor
timestamp: December 29, 2018, 10:07:35 pm
content: HiIs it possible to turn off the displays on Datron 1281 to save VFDs?Thank you

author: pelule
author_rank: Frequent Contributor
timestamp: December 29, 2018, 10:17:04 pm
content: IMHO there is o way by SW/GPIB.But I remember a thread, where one put a switch into the signal bus or supply to switch the display off./PeLuLe

author: Fastah
author_rank: Contributor
timestamp: December 29, 2018, 10:34:33 pm
content: HiInterestingly, Datron did not foresee this option. I've also been thinking about that option.I think, best option will be breaking filaments on both displays... for example pins 1 on both displays... this will save cathode emission on VFDs. Am I right?Thank you

author: Fastah
author_rank: Contributor
timestamp: December 29, 2018, 10:58:29 pm
content: HiI do not prefere drilling case and making modifications adding some switch... this must be unvisible and available from front panel... best solution will be using some combination keys on keyboard for display off and on... for example press and hold key "Sample" and press key "Display"... as I can see this combination does not affect on measuring... maybe some better conbination?Maybe grabbing signals from keyboard and using some digital logic and relay?Better idea?Thank you

author: Fastah
author_rank: Contributor
timestamp: December 30, 2018, 12:49:43 am
content: HiNew better idea..Just checked datasheet of 74c922 keyboard encoder...copy/pasted:A Data Available output goes to a high levelwhen a valid keyboard entry has been made. The DataAvailable output returns to a low level when the enteredkey is released, even if another key is depressed.New idea is press and hold 3 seconds "Monitor" key only for display OFF/ON... status of encoder outputs can be used for activation/deactivation relay or transistor switch... when specific binary state on the encoder outputs holds ex 3 seconds, some digital logic activate or deactivate relay or transistor switch and turn OFF/ON filament on the VFD... default (power on) state must be ONWhat do you think?Thank you

author: doktor pyta
author_rank: Frequent Contributor
timestamp: December 30, 2018, 09:07:56 am
content: https://www.eevblog.com/forum/repair/datron-1271-repair/msg1344045/#msg1344045
Datum / Symmetricom ExacTime 6500 upgrade from TCXO to OCXO - Page 1
Forum section: electronics / general

author: jfphp
author_rank: Regular Contributor
timestamp: January 06, 2019, 05:52:01 pm
content: Hello,I have got a Datum / Symmetricom ExacTime 6500 fitted with a TCXO and I would like to upgrade it with an OCXO. Board has the place with holes to solder it, there are instructions for jumpers but what is the part number of the OCXO ? There are a lot of Datum/ Symetricom OCXO on EBay but what is the right part ? I haven't found in the various manuals on the net. Thank you.

author: EOC_Jason
author_rank: Contributor
timestamp: January 11, 2019, 08:43:51 pm
content: It's been many years since I had an Exactime (and I really don't remember what the inside looked like or the menus), but if their design is in any way similar to the Tymserve then the normal OCXO used is a MTI 240-0530-D. There has been a few posts & links to a couple people doing TCXO to OCXO conversions with tymerves on the time-nuts list, you might want to sift through the mailing list archives as that would probably yield the best info. I'm attaching some pics from a couple different tymserves (one OCXO, one TCXO).
How to use properly DMM - dB mode? - Page 1
Forum section: electronics / general

author: 001
author_rank: Super Contributor
timestamp: December 20, 2018, 02:24:51 pm
content: HiIt may be stupid questionBut tell me please how I can measure audio levels with DMMThanx

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 20, 2018, 02:49:01 pm
content: dB always implies a reference voltage or power. If your meter has a dB scale, it will either default to some value, say 1 mW and 600 ohms (use ohms law to see what voltage that is), or it will let you zero the meter at a specific value. For those, you might decide 1 Vrms is the reference level. You set the signal to that level and hit the zero button. Then the meter reads everything in dB, above or below that level. Voltmeters will use the voltage form of dB, 20*Log(E1/E2).

author: GeoffreyF
author_rank: Regular Contributor
timestamp: December 20, 2018, 03:16:02 pm
content: You can look up what a decibel is.
Time electronics 5051 calibrator - Page 1
Forum section: electronics / general

author: PTR_1275
author_rank: Frequent Contributor
timestamp: December 22, 2018, 12:12:34 am
content: Does anyone have any experience with the Time Electronics range of calibrators? Just curious to get peoples opinions on them if they’ve used them / looked at them.I have a 5051 on my bench at the moment that was having issues with the internal PC that runs the whole thing. Customer service from Time has been pretty good, but unfortunately they won’t do repairs or upgrades on units more than 10 years old.Internally the thing is a frankenstein of power supplies and cards. Definitely the sort of thing that is hand assembled in their factory. The documentation (connections on the back of the unit etc...) done match what the unit actually has.Quick sanity checks I ran yesterday look ok. Need to let it warm up for a bit and put it through some real tests.

author: TiN
author_rank: Super Contributor
timestamp: December 22, 2018, 12:38:05 am
content: Do post teardown pictures and your results. First thing to do - replace all electrolytic caps. Perhaps bad power is what cause digital brains to go whack?I only have 9823 and postedmy experience here. I'd say they are overly optimistic in specifications.Okay for portable DMM and alike calibrations, but no match to industry standards like Fluke 55xx/57xx or Datron's.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: December 22, 2018, 12:56:45 am
content: Some of the problems was user not remembering how bad windows 2000 is.The internal pc has windows 2000 and only 2 USB ports. The keyboard was recognized by bios but as soon as windows started to load the numlock lights went out and the keyboard stopped responding. Talking to a few people they suggested try a ps2 keyboard. The pc manual I found shows a ps2 header so I made up an adaptor and that got the keyboard working.Next issue was the password, but that turned out to be passwordThen the controller software was loading, would error saying the HV and current boards had issues and the program would close. Those 2 boards connect to the backplane through a ribbon cable that was loose. Plugged it in and all is working.I have a feeling that this was offloaded because things weren’t working, but there were lots of loose connectors inside and it appears that’s all that was wrong with it.The 5051 looks to have a lot of functionality and I can tell it’s worlds apart from fluke. I’ll have a read of your page on the 9823 and see how the 5051 goes once warm. Unfortunately it will be a bit of time before I will get to do real tests because the Christmas’s period then we are going on holidays.I couldn’t find any information from users or internals when I was looking, so it would be good to start something about it. In case anyone is looking, list price is £20,000
How to measure Capasitance and leakage in transformers? - Page 1
Forum section: electronics / general

author: 001
author_rank: Super Contributor
timestamp: December 11, 2018, 02:53:04 pm
content: HiHow to measure Capasitance in transformers?- coil to coil- coil to core- windings itself capAnd how to read leakage (if DC test ok)?Is some standard methods?Thank You

author: Berni
author_rank: Super Contributor
timestamp: December 11, 2018, 03:14:50 pm
content: You stick a capacitance meter between the two things you want to measure.Tho the DC leakage test is often done under high voltage conditions. There are dedicated insulation tester meters for that.

author: 001
author_rank: Super Contributor
timestamp: December 11, 2018, 03:23:26 pm
content: Quote from: Berni on December 11, 2018, 03:14:50 pmIt is not so simplyIf I put capasitance meter between coils it will be mistake since coils have its own inductanceDC leakage is not ok too since I`m looking for AC current across coil-to-coil capasitance

author: Berni
author_rank: Super Contributor
timestamp: December 11, 2018, 03:47:56 pm
content: For capacitance you simply wire the two ends of a coil together, that way you get a short connection to the outside edges of a coil so you get a reasonable capacitance measurement. The middle of the coil doesn't matter because its buried under its own windings.As for testing the current i suppose you can stick a signal generator on there and then test for the current using a multimeter. Since the DC resistance tends to be very high this current would likely be mostly capacitive so you wouldn't gain much more understanding from this unless this for some reason a very important parameter in your design (Do note this is heavily frequency dependent).

author: 001
author_rank: Super Contributor
timestamp: December 11, 2018, 04:10:56 pm
content: Quote from: Berni on December 11, 2018, 03:47:56 pmAny prooflinks? You totally misunderstood me in the leakage part

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 11, 2018, 04:36:33 pm
content: Capacitance between coils is done at a low enough frequency where the self inductance doesn't matter.Self capacitance is done by measuring impedance over frequency, and modeling the equivalent inductance, resistance (core loss) and capacitance. (Typically the equivalent circuit also has a number of RLC elements in parallel, representing skin effect, inter-layer capacitance and other complexities, depending on how complex the transformer is, and how accurate the desired model is.)It can also be predicted using transmission line theory, for which it helps that the transformer was designed from TL theory as well. A conventional windup in violation of good TL design, can still be estimated in part, in this way, but there will be more uncertainty regarding how much worse its bandwidth will be.Tim
New acquisition - resistance "standard" - Page 1
Forum section: electronics / general

author: GregDunn
author_rank: Frequent Contributor
timestamp: December 07, 2018, 07:21:51 pm
content: I know these aren't the highest accuracy or lowest TC resistors you can find, but I thought it was a pretty good bargain for a matched set of 0.01/0.02% components - plenty good enough to check my current stack of bench meters. PRC makes these up regularly and ships them in a multiply-padded box; they are pretty good to deal with, and don't mind selling to individuals.I added tape because the little plastic window doesn't have anything to hold it in place, and if you fumble finger the box you will have precision resistors all over the floor in a heartbeat. There's also no external label, unlike the photos shown on their website:https://www.precisionresistor.com/MC-7-Calibrator.html

author: Johncanfield
author_rank: Regular Contributor
timestamp: December 08, 2018, 12:36:40 am
content: Thanks for that. I'm not a metrology nut but I'm surprised that 0.01% tolerance resistors are only suitable for up to 4.5 digit resolution meters. I'm very tempted to buy one just for fun.

author: DaJMasta
author_rank: Super Contributor
timestamp: December 08, 2018, 03:57:23 am
content: Quote from: Johncanfield on December 08, 2018, 12:36:40 amHigher precision meters don't rely on the raw tolerance, they rely on a measured value for the resistor and then a very low temperature coefficient for very low drift. Most precision metrology stuff isn't too particular on the exact value (though round numbers are nice), but rather depends on that value being verified exactly by a high precision, calibrated source and knowing the drift characteristics and having ways to keep them minimized.These are 5ppm/degC, so they're not bad in the drift department. Maybe if you stuck them in a box with the right connectors and measured them with a calibrated 8.5 digit meter, they could be used as standards for some pretty high end meters.

author: GregDunn
author_rank: Frequent Contributor
timestamp: December 08, 2018, 05:02:54 am
content: If I had access to a high accuracy meter that's exactly what I'd do. As it is, I'm just going to try to hold them at a constant temperature when checking my bench meters and compile a table of standard deviation values so I can get a sense of where they are with respect to each other.
Datron 1281 error 2893 repair - Page 1
Forum section: electronics / general

author: syau
author_rank: Frequent Contributor
timestamp: November 22, 2018, 08:14:44 am
content: My Datron 1281 developed an error 2893 which points to the Ohms assembly after I return from vacationSwitching in pathway 056 and found the system giving a value of 0.010078. I tried to do a internal source cal but it end up to the same error 2863. I have swapped the M201 and M202 (DG211CJ) with the same resultCould anybody please share the the value of pathway 056.

author: doktor pyta
author_rank: Frequent Contributor
timestamp: November 22, 2018, 02:40:54 pm
content: On my D1281, P056 gives +0.010025V (last digit unstable).Don't give up

author: syau
author_rank: Frequent Contributor
timestamp: November 26, 2018, 09:53:45 am
content: Dear doktor pyta, thanks for the info.Did some measurements on the resistor R209 and R210 found within limit. Cleaned the board with IPA yield the same result. Will do a external cal later as suggest by another member.

author: pelule
author_rank: Frequent Contributor
timestamp: December 05, 2018, 12:15:16 pm
content: I am sorry to post that late, but I was offline due to a surgery some time.I just read your post.This error occurs when the internal sources have drifted over time.You just need to due a "internal source calibration" to solve that problem.+ Enable calibration (key)+ go to cal menue+ select ext cal+ quit (do not execute)+ next you will be asked if you want to do the internal source calibration - trigger itBut the 1281 must be powered on at least 48hrs to ensure thermal stabilisation.Thats the way to continue operating over long periods without calibration./PeLuLe

author: syau
author_rank: Frequent Contributor
timestamp: December 06, 2018, 03:38:12 am
content: Thanks pelule for the tipsand the self test now passed.