Gossen Metrahit 28S - Page 1
Forum section: electronics / testgear

author: Lunasix
author_rank: Regular Contributor
timestamp: January 19, 2014, 11:35:57 am
content: As another topic presents a Metrahit 25S, here is the 28S, for comparison.

author: BravoV
author_rank: Super Contributor
timestamp: January 19, 2014, 11:41:43 am
content: Wow ... quite surprise to see that hanging 2 Mhz crystal without any firm support, and just relying on it's two soldered pins.Not a very convincing for long term reliability against mechanical vibration, isn't it ?Is it new ?

author: SeanB
author_rank: Super Contributor
timestamp: January 19, 2014, 11:48:35 am
content: That really should have a tiny double sided tape hold down. Better than the usual hot snot or silicone, and just as reliable.

author: BravoV
author_rank: Super Contributor
timestamp: January 19, 2014, 11:50:40 am
content: Quote from: SeanB on January 19, 2014, 11:48:35 amAlthough unlikely with this battery/low power circuit, what if the big ic below it heated up ?Still a poor design imo, especially for this kind of pricey meter.

author: Wytnucls
author_rank: Super Contributor
timestamp: January 19, 2014, 11:55:13 am
content: The meter is discontinued. This particular one has a March 2002 calibration certificate.They age quite well, as long as they are kept in their rubber holsters.My 26S from 2006 looks brand new too.Most of the crystals on these meters are free standing. Doesn't seem to affect reliability.

author: robert_
author_rank: Regular Contributor
timestamp: April 24, 2017, 04:22:48 pm
content: Sadly calibration requires some software that only GMC seems to have. As far as i know, there is no possibility for stand-alone calibration.It is done over the bidirectional IR port.Oh, i just saw it actually is availible for sale at just around 4.5k. (Gossen Metrawatt Z211F)I really wonder why that piece of crusty old software has not yet been umm, liberated or reverse engineered in some way.If there is a installation file floating around, patching out that licence file check probably isnt too hard...Only other problem is it requires some pretty pricey Fluke calibrator (well, you do need some pretty pricey hardware to calibrate a 0.025% multimeter after all) to do anything productive.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 24, 2017, 09:06:18 pm
content: Holly !$!%$^^ that's not fun at allunless finding a leaked iso i'm in no luckThere a demo at Gossen but it wont simulate the 28S ...

author: robert_
author_rank: Regular Contributor
timestamp: April 25, 2017, 01:37:09 pm
content: All that still wont help you unless you find a supported fluke 55xx calibrator to put that software to use.You need some suitably accurate multifunction calibrator anyway. Manual calibration using a standard cell, KVD and loads of reference resistors and other things you also would need to have in the first place hasnt been a thing for many, many years.Same thing with Fluke and all others. Everything a bit beyond really crappy 3 1/2 digit cheapies with a single trimpot has been software cal (using some all in one calibrator) only in the last 20 years.So yes, you would need to have it calibrated at some cal lab, even though its expensive.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 04, 2017, 02:44:23 am
content: the cpus aretmp87ps64f otp cpu, the one with the fw version, i have a 1.52 ??gmcad30 under the crystal, maybe a custom one ??hd61602 lcd driver as shown

author: DrGEM
author_rank: Newbie
timestamp: August 06, 2022, 09:16:08 am
content: There is a device after oxidation of batteries and broken wires. Can anyone at hand suggest the correct location of the charging wires and batteries. Thanks

author: coromonadalix
author_rank: Super Contributor
timestamp: April 13, 2024, 04:29:37 pm
content: late to replyThe calibration SW can be bought for a hefty price, but as written, you need cal equipment connected to it ...have a new puppyv1.52 ??here's my wiring (attached pictures)since mine has black dial overlay is it more recentor older vs the green one sn is LAXXXXno hanging crystaland the charging port plug has a nut ??

author: Taimer81
author_rank: Regular Contributor
timestamp: April 27, 2025, 01:10:41 pm
content: Hello everyone. Were there no opportunities to calibrate this multimeter yourself?

author: coromonadalix
author_rank: Super Contributor
timestamp: April 27, 2025, 10:51:20 pm
content: I repeatthey are software calibrated, you can buy the software for $$$ but you need Fluke calibrators, it talk with themsend it to a cal lab and be done with it ... for the lowest possible price

author: Taimer81
author_rank: Regular Contributor
timestamp: April 29, 2025, 09:23:17 am
content: Quote from: robert_ on April 24, 2017, 04:22:48 pmPlease tell me how much it costs to calibrate this multimeter?

author: coromonadalix
author_rank: Super Contributor
timestamp: April 29, 2025, 09:39:10 am
content: you do the search and requests, it depends of what cal labs you have in your country or next to itsearch for Gossen authorized cal labsin Canada it's 160 CAD whatever the Metrahit model ...

author: Taimer81
author_rank: Regular Contributor
timestamp: April 29, 2025, 09:52:40 am
content: Quote from: coromonadalix on April 29, 2025, 09:39:10 amThank you. The nearest laboratory is located in Turkey. I wrote to them about how much it will cost and the possibility of sending it by mail.

author: Taimer81
author_rank: Regular Contributor
timestamp: April 29, 2025, 10:32:51 am
content: Quote

author: Taimer81
author_rank: Regular Contributor
timestamp: May 13, 2025, 05:21:13 pm
content: Quote from: coromonadalix on April 13, 2024, 04:29:37 pmHello!Please tell me why you need this ?Thank you.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 14, 2025, 01:53:26 am
content: post your images in jpeg formatneed what exactlyi think you absolutely don't understand some meter structure, and still try to cut short of not sending your meter to calibration labssome may or can be adjustmentsoutside the software needed to calibrate themit does not mean in any ways you're gonna be able to calibrate itbut theses are mostly frequency compensations, since you have adjustable capacitors and coils/inductors, trimpot eh i dont know, and i wont touch itMetrahit 27 series 28s 29s (clones) and 30m ARE software calibrated, other lower models are not full Gossens technology, some may be adjustable manually or not

author: Taimer81
author_rank: Regular Contributor
timestamp: May 14, 2025, 04:58:50 am
content: Quote from: coromonadalix on May 14, 2025, 01:53:26 amAll right. I will upload the images in JPEG format.

author: Taimer81
author_rank: Regular Contributor
timestamp: May 14, 2025, 05:02:49 am
content: Quote from: coromonadalix on May 14, 2025, 01:53:26 amWe do not have any calibration laboratories for Gossen in the country. Customs will not allow Siemens or Gossen equipment to pass due to sanctions. Therefore, I cannot ship the multimeter to another country.For this reason, I am looking for other ways to calibrate multi-meters.

author: Taimer81
author_rank: Regular Contributor
timestamp: May 14, 2025, 05:19:31 am
content: I want to eliminate this error. I thought that the regulators on a multimeter could compensate for it.

author: AVGresponding
author_rank: Super Contributor
timestamp: May 14, 2025, 05:33:54 am
content: Quote from: coromonadalix on May 14, 2025, 01:53:26 amGiven the location of the preset trimpot, I wouldn't be surprised if it's for LCD contrast.

author: Taimer81
author_rank: Regular Contributor
timestamp: May 14, 2025, 07:44:37 am
content: It looks like they have sent me a refurbished multimeter.

author: Taimer81
author_rank: Regular Contributor
timestamp: May 14, 2025, 07:47:14 am
content: Quote from: AVGresponding on May 14, 2025, 05:33:54 amThere are 4 trimming resistorson the board. It would be interesting to find out what they are used for.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 14, 2025, 09:39:35 am
content: i think once again you dont know what you are talking about, there are 2 variable capacitors and one inductance and maybe the trimpot is for the contrast adjsutment, since it is near the display / mcu processorthe refurbish you say, could have been some bad re-solderings or if this ic (it is the ASIC / special multimeter ic) have been changed, a calibration is neededi think you bought this meter without knowing what are the implications of such models, and if it is a Siemens, you surely bought it on ebay, there is a seller in Germany who sell themi bought my Siemens from him ... i have the same model and an original 28s too.

author: newbrain
author_rank: Super Contributor
timestamp: May 14, 2025, 11:19:19 am
content: Quote from: Taimer81 on May 14, 2025, 05:19:31 amThe fact is, according to the 28S manual and assuming a perfectly adjusted calibrator, all those reading are inside the characteristic values.Yes, all a bit on the low side, but still in spec.Code:Cal: 0.99999 VReading: 0.99975 VΔ counts: -25Range: 3 V0.02% of reading: 200 µV0.005% of range: 150 µV5 counts: 50 µV--------------------------Total: ±400 µVTotal counts: ±40Cal: 5.0000 VReading: 4.9988 VΔ counts: -12Range: 30 V0.02% of reading: 1.0 mV0.005% of range: 1.5 mV5 counts: 0.5 mV--------------------------Total: ±3.0 mVTotal counts: ±30Cal: 10.0000 VReading: 09.9976 VΔ counts: -24Range: 30 V0.02% of reading: 2.0 mV0.005% of range: 1.5 mV5 counts: 0.5 mV--------------------------Total: ±4.0 mVTotal counts: ±40

author: AVGresponding
author_rank: Super Contributor
timestamp: May 14, 2025, 11:51:25 am
content: fmob was that soldering done by a chimpanzee, wearing boxing gloves?

author: Taimer81
author_rank: Regular Contributor
timestamp: May 14, 2025, 11:55:26 am
content: Quote from: AVGresponding on May 14, 2025, 11:51:25 amI do not know. I just bought this multimeter on eBay yesterday. I opened it and saw that the seller had not told me that the meter was repaired. But right now there is nothing you can do about it. It seems that the work quality was low and the person doing it was too lazy to clean after themselves.

author: Taimer81
author_rank: Regular Contributor
timestamp: May 14, 2025, 03:59:07 pm
content: Quote from: coromonadalix on May 14, 2025, 09:39:35 amYes, you're right. Do you think you should clean the board with alcohol? Or is it better to not touch it? Flux residues. Thank You.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 14, 2025, 04:33:50 pm
content: if you're good at soldering i would redo themBUTwe know here, and have a say here : if it works don't touch it, you need anti static stuff like gloves ...just close it and don't play in it, you received proof that your meter is still in spec at the lower end limit, but still okaytheses Gossens are fancy meters and not repairable most of the time, maybe that meter was serviced way before your purchase, but was not cleaned properly,or else someone tried or managed to re solder the ic because of bad contacts or intermittent problemsfor sure theses solders are not beautiful and messy with the flux ... but once again it works,just close it and leave it as it is, the more you play in it, the more you can create problems

author: Taimer81
author_rank: Regular Contributor
timestamp: May 14, 2025, 04:46:09 pm
content: Quote from: coromonadalix on May 14, 2025, 04:33:50 pmThank you for your advice. I will do exactly that. Please tell me what reference voltage source this multimeter uses?

author: AVGresponding
author_rank: Super Contributor
timestamp: May 14, 2025, 05:27:03 pm
content: Can't see one on that side of the board. It may be integrated into that ASIC with the rough soldering

author: coromonadalix
author_rank: Super Contributor
timestamp: May 14, 2025, 07:29:10 pm
content: @Taimer81 i think you should do your own search ... check the part numbers and check for datasheetsThe asic is Gossen proprietary, no datasheet exist for it, in the wild ...

author: Taimer81
author_rank: Regular Contributor
timestamp: May 16, 2025, 06:00:35 am
content: Based on observations, I have noticed that when measuring resistance, 27i more stable and has less noise than 30М, where the readings float.