34461a warm up time vs sdm3065x - Page 1
Forum section: electronics / general

author: kj7e
author_rank: Frequent Contributor
timestamp: May 05, 2017, 05:14:35 pm
content: Just a fun little comparison, curious what the warmup time is on the keyagilsight 34461a (relatively close competitor) compared to the new Siglent sdm3065x is. Hoping someone who has a 34461a could do the same and show their results to compare.The test, take a stable warmed up 10v source and measure the warm up drift from a cold booted 34461a, use the trend chart set to center 10.000v and a span of 300uV. Show the screen shot at 20 min and 30 min to show the warm up time to settle. In my case, the room temp was 73.5 deg F. Just curious what the warm up time comparison is like, nothing scientific here. The 3065 took about 10 min to warm up, then another 10 to 15 to settle.

author: e61_phil
author_rank: Frequent Contributor
timestamp: May 05, 2017, 07:22:18 pm
content: Hi,I see the siglent, only.

author: kj7e
author_rank: Frequent Contributor
timestamp: May 05, 2017, 07:29:06 pm
content: Quote from: e61_phil on May 05, 2017, 07:22:18 pmYes, I don't have access to a 34461a, I was hoping someone else would provide the comparison info. I may not have been clear above.

author: Fsck
author_rank: Super Contributor
timestamp: May 05, 2017, 07:37:45 pm
content: the specs for the sdm3065x are for a 90m warmup time. did you happen to log the full 90m?the 3446x series are specified for a 60m warmup (like my nice 3457).a 3458 is specified for a 4h warmup time.I would actually be interested to know how the warmup time landed on such nice integers.

author: TheSteve
author_rank: Unknown
timestamp: May 05, 2017, 07:53:24 pm
content: I'd take the 10 volt source out of the equation and just short the input and watch it settle as it warms up.

author: kj7e
author_rank: Frequent Contributor
timestamp: May 05, 2017, 07:55:27 pm
content: Quote from: Fsck on May 05, 2017, 07:37:45 pmI did and there was almost no change after 90min or even 2 hours, it came down 10uV. So after 15 min it was fairly solid starting at a room temp of 73.5 deg F.I have a better, more stable vref (Ian Johnston PDVS2) on its way, once its here Ill do some more testing and logging. Really curious what reference they are using in the 3065x, tempted to open it up but hate to break the seal. Dave Jones mentioned he has one in the shop and was thinking it would make a good candidate for a teardown Tuesday. Also going to do some tempco testing on the meter itself. I made a small thermal insulated case with internal temp monitoring for my reference, now to test the meter at various room temps.Edit: Removing the expansion card slot I was able to see the reference is a LM399H.

author: chris_11
author_rank: Contributor
timestamp: May 05, 2017, 07:59:49 pm
content: Why? If you settle around zero you see only the offset drift settling. The reference settling is as important.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 05, 2017, 08:23:51 pm
content: The numbers given in the instructions are just convenient times for which they gives the specs. So more like a typical time for that type of instrument. There is usually no spec für warmup time-constant. Usually the smaller instruments are faster and those without a fan are often slower.How much the output actually changes can very much depend on the unit. Some will dirft up, some will drift down. For many parts the specs a more like an TC within a +- xxxppm/K range, so the sign and size can vary a low. It is only the heated reference like LM399 / LTZ1000 that have a reasonable well defined change on warmup. It is only the time constant that can be reasonably consistent, though it can be more than just a simple exponential decay type.

author: tautech
author_rank: Super Contributor
timestamp: May 05, 2017, 10:24:16 pm
content: Quote from: kj7e on May 05, 2017, 07:55:27 pmGreat, then I don't have to break the seal on mine either.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: May 06, 2017, 06:11:03 am
content: About 20 ppm in 30 minsdm3065x is drifting like a hell.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 06, 2017, 07:22:06 am
content: Quote from: Mickle T. on May 06, 2017, 06:11:03 amThe drift in the very few first minutes is not important - this is normal, as the reference will need some time to get a stable temperature and there can be also capacitors that need charging. This is especially true for an oven reference.With an LT1000 based reference, in the first 5 minutes the change should be more than 1000 ppm. It is less with the LM399, but still just stabilizing the controlled temperature. It is only a longer boot time that could reduce the initial drift. So if at all one could complain about not having a warmup message for the first 5 minutes or so.

author: TiN
author_rank: Super Contributor
timestamp: May 06, 2017, 07:35:07 am
content: QuoteIf that's typo and related to LTZ1000, all references I had settle to <10ppm under a first minute and then <3ppm for next 5-10 minutes. Just 5c.On topic - if you doing measurements which require the very best accuracy, it's good idea to leave meter, cables, source and everything involved rest for hour or two, to make sure all reached stable condition. Even if you already have warmed up meter (e.g. I have meters 24/7), if you touch cable or swap terminals - there will be induced drift from jacks temperature change. Usual practice wait some minutes after cabling change to level that out.

author: 2N3055
author_rank: Super Contributor
timestamp: May 06, 2017, 09:45:42 am
content: I think I'm a bit confused here, and not only one...First, this is complex instrument. Warmup drift is for the complete complex electro-thermal system, not only for reference circuit. So comparing stabilization times between instrument and reference alone is not relevant, except as an interesting factoid.Also 20 ppm drift from dead cold to full spec is not a problem at all.. Heated reference alone, depending on specimen, room temp and such, can drift many hundreds of ppm in just first few seconds. It's warming up 40-60C over room temp.. It's gonna drift...Also we shouldn't confuse drift amplitude of absolute drift from cold to warm, with converging difference to specified voltage per time. Or to explain it better, if you look at the graph, it shows that it was less than 10 ppm in 2 minutes, less than 6 ppm in 4 min and less than 5 ppm in 6 min.. Long term it is fluctuating +-1 ppm , probably tempco and noise....On most meters, while in boot, it's going to drift many tens ppm's .. But you wont see it...(like Kleinstein said).Also, like TiN says, good practice commands that you need to leave everything to temperature settle for some time (even cables) before measuring....Just mine 5c..Regards to all..

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 06, 2017, 10:29:57 am
content: OK,instead of speculations, here are some real measurements on warmup behavior of LTZ1000, 45°C / 12V heater, LM399H, 90°C / 15V heater, and 34465A Ohm range (similar to 34461A, as both contain LM399 and probably equivalent Ohm circuitry).The LTZ1000s oven needs about 20sec to warm up within + 3.6ppm. The deviation at 20°C is about -900ppm, so the estimated T.C. is about +36ppm/K.It takes about 5minutes to settle to 1ppm, the drift over the next hours is more or less related to the whole circuitry (Andreas PCB and design)The LM399H needs about 15 sec to settle to < 4ppm, the T.C. of its reference is about -4ppm/K.This setup on a breadboard is not so stable, I would guess, that on a PCB, it takes about 10min to settle to 1ppm.Inside a complete instrument, it takes about 1/2h to settle to < 1ppm.. that I observed on my 34465A as well as on my 3458A.Here's the Ohm mode shown, the volt mode should behave the same, but might be more stable after the first hour.Rem.: The 34465As 10kOhm mode can be as stable as < +/- 0.5ppm over 12h, if stabilized for 1/2 day, and ACAL done once.Frank

author: kj7e
author_rank: Frequent Contributor
timestamp: May 08, 2017, 12:39:21 am
content: Some Temp data on the sdm3065x, not sure I figured the ppm drift correctly, please verify.